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Sciences 
Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  NY.  14580 

(716)  872-4503 


Qx. 


CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


M 

Canadian  Institute  for  Historical  Microreproductions  /  Institut  canadien  de  microreproductions  historiques 


Technical  and  Bibliographic  Notes/Notes  techniques  et  bibliographiques 


The  Institute  has  attempted  to  obtain  the  best 
original  copy  available  for  filming.  Features  of  this 
copy  which  may  be  bibliographically  unique, 
which  may  alter  any  of  the  images  in  the 
reproduction,  or  which  may  significantly  change 
the  usual  method  of  filming,  are  checked  below. 


D 


D 


D 


n 


n 


Coloured  covers/ 
Couverture  de  couleur 


I      I    Covers  damaged/ 


Couverture  endommagde 


Covers  restored  and/or  laminated/ 
Couverture  restaurde  et/ou  pellicul^e 


I      I    Cover  title  missing/ 


Le  titre  de  couverture  manque 


I      I    Coloured  maps/ 


Cartes  gdographiques  en  couleur 


Coloured  ink  (i.e.  other  than  blue  or  black)/ 
Encre  de  couleur  (i.e.  autre  que  bleue  ou  noire) 


I      I    Coloured  plates  and/or  illustrations/ 


Planches  et/ou  illustrations  en  couleur 

Bound  with  other  material/ 
Reli§  avec  d'autres  documents 

Tight  binding  may  cause  shadows  or  distortion 
along  interior  margin/ 

La  reliure  serr^e  peut  causer  de  I'ombre  ou  de  la 
distortion  le  long  de  la  marge  intdrieure 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
li  se  peut  que  certaines  pages  blanches  ajoutSes 
lors  d'une  restauration  apparaissent  dans  le  texte, 
mais,  lorsque  cela  6tait  possible,  ces  pages  n'ont 
pas  dtd  filmdes. 

Additional  comments:/ 
Commentaires  suppl6mentaires; 


L'Institut  a  microfilm^  le  meilleur  exemplaire 
qu'il  lui  a  6X6  possible  de  se  procurer.  Les  details 
de  cet  exemplaire  qui  sont  peut-dtre  uniques  du 
point  de  vue  bibliographique,  qv\  peuvent  modifier 
une  image  reproduite,  ou  qui  peuvent  exiger  une 
modification  dans  la  m6thode  normale  de  filmage 
sont  indiquds  ci-dessous. 


I      I    Coloured  pages/ 


n 

D 

0 


Pages  de  couleur 

Pages  damaged/ 
Pages  endommagdes 

Pages  restored  and/or  laminated/ 
Pages  restaur^es  et/ou  pellicul^es 

Pages  discoloured,  stained  or  foxed/ 
Pages  d^colordes,  tachetdes  ou  piqu^es 

Pages  detached/ 
Pages  d^tach^es 

Showthrough/ 
Transparence 


I      I    Quality  of  print  varies/ 


Quality  indgale  de  I'impression 

Includes  supplementary  material/ 
Comprend  du  materiel  supplementaire 


Only  edition  av^iilable/ 
Seule  Edition  disponible 

Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc.,  have  been  refilmed  to 
ensure  the  best  possible  image/ 
Les  pages  totalement  ou  partiellement 
obscurcies  par  un  feuillet  d'errata,  une  pelure, 
etc.,  ont  6t^  film^es  d  nouveau  de  fapon  d 
obtenir  la  meilleure  image  possible. 


This  item  is  filmed  at  the  reduction  ratio  checked  below/ 

Ce  document  est  filmd  au  taux  de  reduction  indiqu6  ci-dessous. 


10X 

14X 

18X 

22X 

26X 

SOX 

1 

v/ 

12X 


16X 


20X 


24X 


28X 


32X 


The  copy  filmed  here  has  been  reproduced  thanks 
to  the  generosity  of: 


Library, 

Geological  Survey  of  Canada 


L'exemplaire  filmd  fut  reproduit  grSce  d  la 
gin^rositd  de: 

Bibliotheque, 

Commission  Giologique  du  Canada 


The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legibility 
of  the  original  copy  and  in  keeping  with  the 
filming  contract  specifications. 


Original  copies  in  printed  paper  covers  are  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  illustrated  impres- 
sion, or  the  back  cover  when  appropriate.  All 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  impres- 
sion, and  ending  on  the  last  page  with  a  printed 
or  illustrated  impression. 


The  last  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  —h^  (meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 

Maps,  plates,  charts,  etc.,  may  be  filmed  at 
different  reduction  ratios.  Those  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hand  corner,  left  to 
right  and  top  to  bottom,  as  many  frames  as 
required.  The  following  diagrams  illustrate  the 
method: 


Les  images  suivantes  ont  6t6  reproduites  avec  le 
plus  grand  soin,  compte  tenu  de  la  condition  et 
de  la  nettet6  de  l'exemplaire  film6,  et  en 
conformity  avec  les  conditions  d'*  contrat  de 
filmage. 

Les  exemplaires  originaux  dont  la  couverture  en 
papier  est  imprim^e  sont  film^s  en  commenpant 
par  le  premier  plat  et  en  terminant  soit  par  la 
dernidre  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration,  soit  par  le  second 
plat,  selon  le  cas.  Tous  les  autres  exemplaires 
originaux  sont  film6s  en  commenpant  par  la 
premidre  page  qui  comporte  :«ne  empreinte 
d'impression  ou  d'illustration  et  eri  terminant  par 
la  dernidre  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboles  suivants  apparaitra  sur  la 
dernidre  image  de  cheque  microfiche,  selon  le 
cas:  le  symbole  — »>signifie  "A.  SUIVRE",  le 
symboie  V  signifie  "FIN". 

Les  cartes,  planches,  tableaux,  etc.,  peuvent  6tre 
film^s  d  des  taux  de  reduction  diffdrents. 
Lorsque  le  document  est  trop  grand  pour  dtre 
reproduit  en  un  seul  clich6,  il  est  film6  d  partir 
de  Tangle  sup^rieur  gauche,  de  gauche  d  droite, 
et  de  haut  en  bas,  en  prenant  le  nombre 
d'images  ndcessaire.  Les  diagrammes  suivants 
illustrent  la  mdthode. 


1 

2 

3 

32X 


1 

2 

3 

4 

5 

6 

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010203 

THE   INTERNATIONAL  SCIENTIFIC  SERIBS  'o^^'^'^^'  **•• 


THE 


C 


GEOLOGICAL  HISTORY 
OF  PLANTS 


BY 


SIE  J.  WILLIAM  DAWSON 

C.  M.  O.,  LL.  D.,  F.  R.  S.,  &c. 


WITH  ILLUSTRATION 


'.  •   •  •  - 


N^^W    YORK 
D.    APPLEx.,.^    Af^D    COMPANY 

1888 


COPYEIOHT,  1888, 

By  D.  APPLETON  AND  COMPANY. 


«    t   «  C  <  '• 


1  •-< 


j 


PREFACE. 


The  object  of  tliis  work  is  to  give,  in  a  connected 
form,  a  summary  of  the  development  of  the  vegetable 
kingdom  in  geological  time. 

To  the  geologist  and  botanist  the  subject  is  one  of 
importance  with  reference  to  their  special  pursuits,  and 
one  on  which  it  has  not  been  easy  to  find  any  conveni- 
ent manual  of  information.  It  is  hoped  that  its  treat- 
ment in  the  present  volume  will  also  be  found  suffi- 
ciently simple  and  popular  to  be  attractive  to  the 
general  reader. 

In  a  work  of  so  limited  dimensions,  detailed  descrip- 
tions cannot  be  given,  except  occasionally  by  way  of 
illustration ;  but  references  to  authorities  will  be  made 
in  foot-notes,  and  certain  details,  which  may  be  useful  to 
collectors  and  students,  will  be  placed  in  notes  appended 
to  the  chapters,  so  as  not  to  encumber  the  text. 

The  illustrations  of  this  work  are  for  the  most  part 
original ;  but  some  of  them  have  previously  appeared 
in  special  papers  of  the  author. 

J.  W.  D. 

February,  1888. 


•^'T^t^ 


h 


COI^TENTS. 


CHAPTER   I. 


PA6B 


Preliminary  Ideas  of  Geolooical  Chronology  and  of  the  Classi- 
fication OF  Plants 1 

CHAPTER   II. 

Vegetation  of  tue  Lacrentian  and  Early  Paleozoic — Questions 

AS  TO  Alg^ 8 

CHAPTER    III. 

The  Erian  or  Dkvonian   Forests — Origin   of    Petroleum— The 
AoE  of  Acrogens  and  Gymnosperms 45 

CHAPTER    lY. 

The  CARBONiFERotis  Flora  -Culmination  ok  the  Acrooens — For- 
mation OF  Coal 110 

CHAPTER  V. 

The  Flora  of  the  Early  Mesozoic — Reign  of  Pines  and  Cycads  .  175 


CHAPTER   VI. 

The  Reign  of  Angiosperms  in  the  Later  Cretaceous  and  Early 

Tertiary  or  Kainozoic 191 

2 


Nlf 


'  'HWiiniiin'11— tWM 


•  •  • 

Vlll 


CONTENTS. 


CHAPTER   VII. 
Plants  from  the  Tertiary  to  thk  Modern  Plriod 


PAGE 

.  219 


CHAPTER   VIII. 

Geneuai.,  Laws  op  Origin  and  Migrations  op  Plants — Relat'ons 
OP  Recent  and  Fossil  Flouas 287 

APPENDIX. 

I.  Comparative  View  of  PALiEozoic  Floras       ....  273 

II.  Hekr's  Latest  Statements  on  the  Greenland  Flora    .        .  281 

III.  Mineralisation  of  Fossil  Plants 284 

IV.  General  Works  on  Paleobotany 286 


t 


LIST   OF  ILLUSTEATIOI^S. 


PAOB 

Table  op  Chronology  op  Plants  ....    (Frontispiece.) 

Protannularia  Harkncssii 21 

Nematophvton  Logani  (three  Figures) 22,  23 

Trail  of  K!ng-Crab 28 

Trail  of  Carboniferous  Crustacean 28 

Rusichnitcs 29 

PaliPophyciis 30 

Astropolithon 31 

Carboniferous  Rill-mark 33 

Cast  of  Shrinkage  Cracks 34 

Cone-in  cone 36 

Buthotrephis Si 

Silurian  Vegetation 40 

Brian  Plants 49 

Protosalvinia 64 

Ptilophyton  (two  Figures) 62,  63 

Psilophyton  (two  Figures) 64,  66 

Sphenophyllum 66 

Lcpido>'endron 66 

Various  ..  cms 72,73 

ArcluTopteris 74 

Cauloptcris 75 

Megalopteris 76 

Calamites 77 

Asterophyllites         .        .         , 78 

Dadoxylon ,,,...  79 


LIST  OF   ILLUSTRATIONS. 


fl 


i 
ii 


Species) 


Cordaites         .... 

Erian  Fruits     .... 

Foliage  from  th(^  Coal -formation 

Sigillaria!  (five  Figure.^)    . 

Stigmariie  (two  Figures)  . 

Vcgt'tiible  Tissues    . 

Coals  and  Erect  Trees  (two  Figures) 

Lepidodendron 

Lepidophloios  .... 

Astcropliyllites,  &c. . 

Calamitcs  (five  Figure.='>    . 

Ferns  of  the  Coal-formaiion  (six  Figures) 

Noeggcratliia  dispar 

Cordaites         .... 

Fruits  of  Cordaites,  &c.    . 

Conifers  of  the  Coal-formation  (four 

Trigonocarpum 

Sternberg!  a      .... 

Walfliia  imbricatula 

Foliage  of  the  Jurassic  Period  . 

Podozamites     .... 

Salisburia         .... 

Sequoia    ..... 

Populus  primieva 

Stercalia  and  Laurophyllum 

Vegetation  of  the  Cretaceous  Period 

Platanus  ..... 

Protophylluni  .... 

Magnolia  .... 

Liriodendron  (two  Figures) 

Brasenia 

Gaylussaccia  resinosa 

Populus  balsamifera 

Fucus      


PAGE 

.  81 
.  82 
.  VI 

112-114 
.  115 
.  117 

118,  119 
.  120 
.  121 
.  122 

123-125 

12G-129 
.   130 


131 
132 
135 
136 
137 
138 
177 
178 
180 
181 
191 
194 
195 
19S 


199 
200 
201 
207 
228 
229 
230 


THE 


GEOLOGICAL    HISTORY  OF   PLANTS. 


CHAPTER  I. 

PRELIMINARY   IDEAS   OF  GEOLOGICAL   CHRONOLOGY   AND 
OF  THE  CLASSIFICATION   OF   PLANTS. 


The  knowledge  of  fossil  plants  and  of  the  history  of 
the  vegetable  kingdom  has,  until  recently,  been  so  frag- 
mentary that  it  seemed  hopeless  to  attempt  a  detailed 
treatment  of  the  subject  of  this  little  book.  Our  stores 
of  knowledge  have,  however,  been  rapidly  accumulating 
in  recent  years,  and  we  have  now  arrived  at  a  stage  when 
every  new  discovery  serves  to  render  useful  and  intelligi- 
ble a  vast  number  of  facts  previously  fragmentary  and  of 
uncertain  import. 

Tlie  writer  of  this  work,  born  in  a  district  rich  in 
fossil  plants,  began  to  collect  and  work  at  these  as  a 
boy,  in  connection  with  botanical  and  geological  pursuits. 
He  has  thus  been  engaged  in  the  study  of  fossil  plants 
for  nearly  half  a  century,  and,  while  he  has  published 
much  on  the  subject,  has  endeavoured  carefully  to  keep 
within  the  sphere  of  ascertained  facts,  and  has  made  it 
a  specialty  to  collect,  as  far  as  possible,  what  has  been 
published  by  others.  He  has  also  enjoyed  opportunities 
of  correspondence  or  personal  intercourse  with  most  of 


\ 


a 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


i: 


the  more  eminent  workers  in  the  subject.  No'v.  in  the 
evening  of  his  days,  he  thinks  it  right  to  endeavour  to 
place  before  the  world  a  summary  of  facts  and  of  his  own 
matured  conclusions— feeling,  however,  that  nothing  can 
be  final  in  this  matter  ;  and  that  he  can  only  hope  to 
sketch  the  present  aspect  of  the  subject,  and  to  point  the 
way  to  new  developments,  which  must  go  on  long  after 
he  shall  have  passed  away. 

The  subject  is  one  which  has  the  disadvantage  of  pre- 
supposing some  knowledge  of  the  geological  history  of 
the  earth,  and  of  the  classification  and  structures  of  mod- 
ern plants ;  and  in  order  that  all  who  may  please  to  read 
the  following  pages  may  be  placed,  as  nearly  as  possible, 
on  the  same  level,  this  introductory  chapter  will  be  de- 
voted to  a  short  statement  of  the  general  facts  of  geological 
chronology,  and  of  the  natural  divisions  of  the  vegetable 
kingdom  in  their  relations  to  that  chronology. 

The  crust  of  the  earth,  as  we  somewhat  modestly  term 
that  portion  of  its  outer  shell  which  is  open  to  our  obser- 
vation, consists  of  many  beds  of  rock  superimposed  on 
each  other,  and  which  must  have  been  deposited  succes- 
sively, beginning  with  the  lowest.  This  is  proved  by  the 
structure  of  the  beds  themselves,  by  the  markings  on 
their  surfaces,  and  by  the  remains  of  animals  and  plants 
which  they  contain  ;  all  these  appearances  indicating  that 
each  successive  bed  must  have  been  the  surface  before  it 
was  covered  by  the  next. 

As  these  beds  of  rock  were  mostly  formed  under  water, 
and  of  material  derived  from  the  waste  of  land,  they  are 
not  universal,  but  occur  in  those  places  where  there  were 
extensive  areas  of  water  receiving  detritus  from  the  land. 
Further,  as  the  distinction  of  land  and  watei  arises  prima- 
rily from  the  shrinkage  of  the  mass  of  the  earth,  and 
from  the  consequent  collapse  of  the  crust  in  some  places 
and  ridging  of  it  up  in  others,  it  follows  that  there  have, 
from  the  earliest  geological  periods,   been  deep  ocean- 


GEOLOGICAL  CHRONOLOGY. 


8 


basins,  ridpefc.  of  elevated  land,  and  broad  plateaus  inter- 
vening bctweeii  the  lidges,  and  which  were  at  some  times 
under  water,  and  ut  otlier  times  land,  with  many  inter- 
mcdiato  phases.  The  settlement  and  crumpling  of  the 
crust  were  not  continuous,  but  took  place  at  intervals ; 
and  each  such  settlement  produced  not  only  a  ridging  up 
along  certain  lines,  but  also  an  emergence  of  the  i)lains 
or  plateaus.  Thus  at  all  times  there  have  been  ridges  of 
folded  rock  constituting  mountain-ranges,  flat  expansions 
of  continental  plateau,  sometimes  dry  and  sometimes  sub- 
merged, and  deep  ocean-basins,  never  except  in  some  of 
their  shallower  portions  elevated  into  land. 

By  the  study  of  the  successive  beds,  more  especially 
of  those  de))Osited  h\  the  times  of  continental  submer- 
gence, we  obtain  a  table  of  geological  chronology  which 
expresses  the  several  stages  of  the  formation  of  the  earth's 
crust,  from  tnat  early  time  when  a  solid  shell  first  formed 
on  our  nascent  planet  to  the  present  day.  By  collecting 
the  fossil  remains  embedded  in  the  several  layers  and 
placing  these  in  chronological  order,  we  obtain  in  like 
manner  histories  of  animal  and  plant  life  parallel  to  the 
physical  changes  indicated  by  the  beds  themselves.  The 
facts  as  to  the  sequence  we  obtain  from  the  study  of  ex- 
posures in  cliffs,  cuttings,  quarries,  and  mines  ;  and  by 
correlating  these  local  sections  in  a  great  number  of  places, 
we  obtain  our  general  table  of  succession  ;  though  it  is  to 
be  observed  that  in  some  single  exposures  or  series  of 
exposures,  like  those  in  the  great  caflons  of  Colorado,  or 
on  the  coasts  of  Great  Britain,  we  can  often  in  one  locality 
see  nearly  the  whole  sequence  of  beds.  Let  us  observe 
here  also  that,  though  we  can  trace  these  series  of  deposits 
over  the  whole  of  the  surfaces  of  the  continents,  yet  if 
the  series  could  be  seen  in  one  spot,  say  in  one  shaft  sunk 
through  the  whole  thickness  of  the  earth's  crust,  this 
would  be  sufficient  for  our  purpose,  so  far  as  the  history 
of  life  is  concerned.  ■,  -.. 


■rt- 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


I 


The  evidence  is  similar  to  that  obtained  by  Schlie- 
mann  on  the  site  of  Troy,  where,  in  digging  through  suc- 
cessive layers  of  debris,  he  found  the  objects  deposited  by 
successive  occupants  of  the  site,  from  the  time  of  the 
Roman  Empire  back  to  the  earliest  tribes,  whose  flint 
weapons  and  the  ashes  of  their  fires  rest  on  the  original 
surface  of  the  ground. 

Lot  us  now  tabulate  the  whole  geological  succession 
with  the  history  of  animals  and  plants  associated  with  it: 


ANIMALS. 


Age  of   Man   and 
Mammalia. 


Age  of  Reptiles. 


Age  of  Arapliibians 
and  Fishes. 
Age  of  Inverte- 
brates. 


Age  of  Protozoa. 


SYSTEMS    OF  FORMATIONS. 


O 
N 
O 

a 
'S 

U4 


Modern, 

Pleistocene, 
-1   Pliocene, 
j  Miocene, 
I  Eocene. 


.2  r 


o 

N 
O 
in 


o 
o 

J 

p. 


o 

N 

o 


Cretaceous, 
i  Jiiras.'^ic, 
Triassic. 

r  Permian, 

j  Carboniferous, 

I  Erian, 

1  Silurian, 

j  Ordovician, 

I  Cambrian, 

I  Il'ironian  (Upper). 

Iluronian  (Lower), 
Upper  Laurcntian, 
Middle  Laurcntian, 
Lower  Laurcntian. 


PLANTS. 


Angiosperms  and 
Palms  dominant. 


Cycads  and  Pines 
dominant. 


Acrogens  and  Gym- 
nosperms  domi- 
nant. 


Protogcns  and 
Algre. 


It  will  be  observed,  since  only  the  latest  of  the  sys- 
tems of  formations  in  this  table  belongs  to  the  period  of 
human  history,  that  the  whole  lapse  of  time  embraced  in 
the  table  must  be  enormous.  If  we  suppose  the  modern 
period  to  have  continued  for  say  ten  thousand  years,  and 
each  of  the  others  to  have  been  equal  to  it,  we  shall  re- 
quire two  hundred  thousand  years  for  the  whole.  There 
is,  however,  reason  to  believe,  from  the  great  thickness  of 
the  formations  and  the  slowness  of  the  deposition  of  many 


^       ! 


GEOLOGICAL  CUROXOLOGY.  5 

of  them  in  the  older  systems,  that  they  must  have  re- 
quired vastly  greater  time.  Taking  these  criteria  into 
account,  it  has  been  estimated  that  the  time-ratios  for 
the  first  three  great  ages  may  he  as  one  for  the  Kainozoic 
to  tiiree  for  tiie  Mesozoic  and  twelve  for  the  Palaeozoic, 
with  as  much  for  the  Eozoic  as  for  the  Pala'ozoic.  This  is 
Dana's  estimate.  Another,  by  Hull  and  Ilougiiton,  gives 
the  following  ratios  :  Azoic,  34*3  per  cent.  ;  Palaeozoic, 
42*5  per  cent.  ;  Mesozoic  and  Kainozoic,  23*2  per  cent. 
It  is  furtlier  held  that  the  modern  jwriod  is  much  siiorter 
than  tiie  other  periods  of  the  Kainozoic,  so  that  our 
geological  table  may  have  to  be  measured  by  millions  of 
years  instead  of  thousands. 

We  cannot,  however,  attach  any  certain  and  definite 
value  in  years  to  geological  time,  but  must  content  our- 
selves Tvith  the  general  statement  that  it  has  been  vastly 
long  in  comparison  to  that  covered  by  human  history. 

Bearing  in  mind  this  great  duration  of  geological  time, 
and  the  fact  that  it  probably  extends  from  a  period  when 
the  earth  was  intensely  heated,  its  crust  thin,  and  its  con- 
tinents as  yet  unformed,  it  will  be  evident  that  the  con- 
ditions of  life  in  the  earlier  geologic  periods  may  have 
been  very  different  from  those  which  obtained  later. 
When  we  further  take  into  account  the  vicissitudes  of 
land  and  water  which  have  occurred,  we  shall  see  that 
such  changes  must  have  produced  very  great  differences 
of  climate.  The  warm  equatorial  waters  have  in  all 
periods,  as  superficial  oceanic  currents,  been  main  agents 
in  the  diffusion  of  heat  over  the  surface  of  the  earth,  and 
their  distribution  to  north  and  south  must  have  been 
determined  mainly  by  the  extent  a»id  direction  of  land, 
though  it  may  also  have  been  modified  by  the  changes  in 
the  astronomical  relations  and  period  of  the  earth,  and 
the  form  of  its  orbit.*     We  know  by  the  evidence  of 


*  Croll,  "  Climate  and  Time." 


THE   GEOLOGICAL   IIISTOKY   OF   PLANTS. 


n      i 


i    i 


fossil  plants  that  chanp;es  of  this  kind  have  occurred  so 
great  as,  on  the  one  hand,  to  j)ermit  the  plants  of  warm 
temperate  re^^ions  to  exist  within  the  Arctic  Circle  ;  and, 
on  the  other,  to  drive  these  i)lants  into  the  tropics  and 
to  replace  them  by  Arctic  forms.  It  is  evident  also  that 
in  those  periods  when  the  continental  ureas  were  largely 
submerged,  there  might  be  an  excessive  amount  of  moist- 
ure in  the  atmosphere,  greatly  modifying  the  climate,  in 
80  far  as  plants  are  concerned. 

Let  us  now  consider  the  history  of  the  vegetable  king- 
dom as  indicated  in  the  few  notes  in  the  right-hand 
column  of  the  table. 

The  most  general  subdivision  of  plants  is  into  the  two 
great  series  of  Cryptogams,  or  those  which  have  no  mani- 
fest flowers,  and  produce  minute  spores  instead  of  seeds ; 
and  Phfcnogams,  or  those  which  possess  flowers  and  pro- 
duce seeds  containing  an  embryo  of  the  future  i)lant. 

The  Cryptogams  may  be  subdivided  into  the  following 
three  groups  : 

1.  Thallof/fitis,  cellular  plants  not  distinctly  distin- 
guishable into  stem  and  leaf.  These  are  the  Fungi,  the 
Lichens,  t^nd  the  Algae,  or  sea-weeds. 

2.  Anogens,  having  stem  and  foliage,  but  wholly  cel- 
lular.    These  are  the  Mosses  and  Liverworts. 

3.  Acrogens,  which  have  long  tubular  fibres  as  well  as 
cells  in  their  composition,  and  thus  have  the  capacity  of 
attaining  a  more  considerable  magnitude.  These  are  the 
Ferns  {Filices),  the  Mare's-tails  {Equisetacem),  i.  i  the 
Club-mosses  {Li/copodiacrcB),  and  a  curious  little  group 
of  aquatic  plants  called  Rhizocarps  {RMzocarpem). 

The  Pha3nogams  are  all  vascular,  but  they  differ  much 
in  the  simplicity  or  complexity  of  their  flowers  or  seeds. 
On  this  ground  they  admit  of  a  twofold  division  : 

1.  Gymnosperms,  or  those  which  bear  naked  seeds 
not  enclosed  in  fruits.  They  are  the  Pines  and  their 
allies,  and  the  Cycads. 


CLASSIFICATION'   OF    PLANTS. 


2.  Atif/iospernis,  wliicli  product'  true  fruits  enclosing 
the  seeds.  In  this  gnnij)  there  are  two  well-marked  sub- 
divisions ditTcriii^  in  the  structure  of  the  seed  and  stem. 
Tlioyare  the  Endo<icnHyOV  inside  growers,  with  seeds  hav- 
ing one  seed-leaf  only,  as  the  grasses  and  the  j)alms ;  and 
the  Krof/pus,  having  outside-growing  woody  stems,  and 
seeds  with  two  seed-leaves.  Most  of  the  ordinary  forest- 
trees  of  temperate  climates  belong  to  this  ^roup. 

On  referring  to  the  geological  table,  it  will  be  seen 
that  there  is  a  certain  rough  correspondence  between  the 
order  of  rank  of  phmts  and  the  order  of  their  apj)earance 
in  time.  The  oldest  plants  that  we  certainly  know  are 
Algtu,  and  with  these  there  are  plants  apparently  with 
the  structures  of  Thallophytes  hut  thj  habit  of  trees,  and 
which,  for  want  of  a  better  name,  I  may  call  Protof/ens. 
Plants  akin  to  the  Rhizocari)s  also  appear  very  early. 
Next  in  order  we  find  forests  in  which  gigantic  Ferns  and 
Lycopods  and  Mare's-tails  predominate,  and  are  assijciated 
with  pines.  Succeeding  these  we  have  a  reign  of  Gym- 
nosperms,  and  in  the  later  formations  we  find  the  higher 
Plunenogams  dominant.  Thus  there  is  an  advance  in 
elevation  and  complexity  along  with  the  advance  in 
geological  time,  but  connected  with  the  remarkable  lact 
that  in  earlier  times  low  groups  attain  to  an  elevation 
unexampled  in  later  times,  when  their  places  are  occu- 
pied with  plants  of  higher  type. 

It  is  this  historical  development  that  we  have  to  trace 
in  the  following  pages,  and  it  will  be  the  most  simple 
and  at  the  same  time  the  most  instructive  method  to 
consider  it  in  the  order  of  time. 


CHAPTER  II. 


I 


': 

J 

1 

'i              ■ 

1 

Iv 

^ 

ii 

\l 

i; 

, 

f 

-M 

1, 

i 

1 

VEGETATION   OF  THE  LAURENTIAN   AND   EARLY   PALiEO- 
ZOIC — QUESTIONS   AS  TO   ALG^. 

Oldest  of  all  the  formations  known  to  geologists,  and 
representing  perhaps  the  earliest  rocks  produced  after  our 
earth  had  ceased  to  be  a  molten  mass,  are  the  hard,  crys- 
talline, and  much-contorted  rocks  named  by  tlie  late  Sir 
W.  E.  Logan  Laurentian,  and  which  are  largely  developed 
in  the  northern  parts  of  North  America  and  Ei'.rope,  and 
in  many  other  regions.  So  numerous  and  extensive,  in- 
deed, are  the  exposures  of  these  rocks,  that  we  have  good 
reason  to  believe  that  they  underlie  all  the  other  forma- 
tions of  our  continents,  and  are  even  world-wide  in  their 
distribution.  In  the  lower  part  of  this  great  system  of 
rocks  which,  in  some  places  at  least,  is  thirty  thousand 
feet  in  thickness,  we  find  no  traces  of  the  existence  of 
any  living  thing  on  the  earth.  But,  in  the  middle  por- 
tion of  the  Laurentian,  rocks  are  found  which  indicate 
that  there  were  already  land  and  water,  and  that  the  waters 
and  possibly  the  land  were  already  tenanted  by  living 
beings.  The  great  beds  of  limestone  which  exist  in  this 
part  of  the  system  furnish  one  indication  of  this.  In  the 
later  geological  formations  the  limestones  are  mostly  or- 
ganic— that  is,  they  consist  of  accumulated  remains  of 
sliells,  corals,  and  other  hard  parts  of  marine  animals, 
which  are  composed  of  calcium  carbonate,  which  the  ani- 
mals obtain  directly  from  their  food,  and  indirectly  from 
the  calcareous  matter  dissolved  in  the  sea-water.     In  like 


LAURENTIAN  AND  EARLY  PALEOZOIC.  9 

manner  great  beds  of  iron-ore  exist  in  the  Laurentian ; 
but  in  later  formations  the  determining  cause  of  the 
accumulation  of  such  beds  is  the  partial  deoxidation  and 
solution  of  the  peroxide  of  iron  by  the  agency  of  organic 
matter.  Besides  this,  certain  forms  known  as  Eozoon 
Canadrnse  have  been  recognised  in  the  Laurentian  lime- 
stones, which  indicate  the  presence  at  least  of  one  of  the 
lower  types  of  marine  animals.  Where  animal  life  is,  we 
may  fairly  \  Iqt  the  existence  of  vegetabV,  life  as  well, 
since  the  plant  is  the  only  producer  of  food  for  the  ani- 
mal. But  we  are  not  left  merely  to  this  inference.  Great 
quantities  of  carbon  or  charcoal  in  the  form  of  the  sub- 
stance known  as  graphite  or  plumbago  exist  in  the 
Laurentian.  Now,  in  more  recent  formations  we  have 
deposits  of  coal  and  bituminous  matter,  and  we  know 
that  these  have  arisen  from  the  accumulation  and  slow 
putrefaction  of  masses  of  vegetable  matter.  Further,  in 
places  where  igneous  action  has  affected  the  beds,  we 
find  that  ordinary  coal  has  been  changed  into  anthracite 
and  graphite,  that  bituminous  shales  have  been  converted 
into  graphitic  shales,  and  that  cracks  filled  with  soft 
bituminous  matter  have  ultimately  become  changed  into 
veins  of  graphite.  When,  therefore,  we  find  in  the  Lau- 
rentian thick  beds  of  graphite  and  beds  of  limestone 
charged  with  detached  grains  and  crystals  of  this  sub- 
stance, and  graphitic  gneisses  and  schists  and  veins  of 
graphite  traversing  the  beds,  we  recognise  the  same 
phenomena  that  are  apparent  in  later  formations  con- 
taining vegetable  debris. 

The  carbon  thus  occurring  in  the  Laurentian  is  not 
to  be  regarded  as  exceptional  or  rare,  but  is  widely  dis- 
tributed and  of  large  amount.  In  Canada  more  especially 
the  deposits  arc  very  considerable. 

The  graphite  of  the  Laurentian  of  Canada  occurs  both 
in  beds  and  in  veins,  and  in  such  a  manner  as  to  show 
that  its  origin  and  deposition  are  contemporaneous  with 
8 


10 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


i    J 


I 

r    ■ 


thog*?  of  the  containing  rock.  Sir  William  Logan  states  * 
that  "  the  deposits  of  plumbago  generally  occur  in  the 
limestones  or  in  their  immediate  vicinity,  and  granular 
varieties  of  the  rock  often  contain  large  crystalline  plates 
of  plumbago.  At  other  times  this  mineral  is  so  finely 
disseminated  as  to  give  a  bluish-grey  colour  to  the  lime- 
stone, and  the  distribution  of  bands  thus  coloured  seems 
to  mark  the  stratification  of  the  rock."  He  further 
states:  **The  plumbago  is  not  confined  to  the  lime- 
stones ;  large  crystalline  scales  of  it  are  occasionally  dis- 
seminated in  pyroxene  rock,  and  sometimes  in  quartzite 
and  in  feldspathic  rocks,  or  even  in  magnetic  oxide  of 
iron."  In  addition  to  these  bedded  forms,  there  are  also 
true  veins  in  which  graphite  occurs  associated  with  cal- 
cite,  quartz,  orthoclase,  or  pyroxene,  and  either  in  dis- 
seminated scales,  in  detached  masses,  or  in  bands  or  layers 
"  separated  from  each  other  and  from  the  wall-rock  by 
feldspar,  pyroxene,  and  quartz."  Dr.  Hunt  also  men- 
tions the  occurrence  of  finely  granular  varieties,  and  of 
that  peculiarly  waved  and  corrugated  variety  simulating 
fossil  wood,  though  really  a  mere  form  of  laminated 
structure,  which  also  occurs  at  Warrensburg,  New  York, 
and  at  the  Marinski  mine  ir  Siberia.  Many  of  the  veins 
are  not  true  fissures,  but  rather  constitute  a  network  of 
shrinkage  cracks  or  segregation  veins  traversing  in  count- 
less numbers  the  containing  rock,  and  most  irregular  in 
their  dimensions,  so  that  they  often  resemble  strings  of 
nodular  masses.  It  is  most  probable  that  the  graphite  of 
the  veins  was  originally  introduced  as  a  liquid  or  plastic 
hydrocarbon  ;  but  in  whatever  way  introduced,  the  char- 
acter of  the  veins  indicates  that  in  the  case  of  the  greater 
number  of  them  the  carbonaceous  material  must  have 
been  derived  from  the  bedded  rocks  traversed  by  these 
veins,  to  which  it  bears  the  same  relation  with  the  veins 


Mi 


•  "  Geology  of  Canada,"  1863. 


LAURENTIAN  AND  EARLY  PALAEOZOIC. 


11 


of  bitumen  found  in  the  bituminous  shales  of  the  Car- 
boniferous and  Silurian  rocks.  Nor  can  there  be  any 
doubt  that  the  graphite  found  in  the  beds  hc^s  been  de- 
posited along  with  the  calcareous  matter  or  muddy  and 
sandy  sediment  of  which  these  beds  were  originally  com- 
posed.* 

The  quantity  of  graphite  in  the  Lower  Lauren tian 
series  is  enormous.  Some  years  ago,  in  the  township  of 
Buckingham,  on  the  Ottawa  Eiver,  I  examined  a  band  of 
limestone  believed  to  be  a  continuation  of  that  described 
by  Sir  W.  E.  Logan  as  the  Green  Lake  limestone.  It 
was  estimated  to  amount,  with  some  thin  interstratified 
bands  of  gneiss,  to  a  thickness  of  six  hundred  feet  or 
more,  and  was  found  to  be  filled  with  disseminated  crys- 
tals of  graphite  and  veins  of  the  mineral  to  such  an  extent 
as  to  constitute  in  some  places  one-fourth  of  the  whole  ; 
and,  making  every  allowance  for  the  poorer  portions,  this 
band  cannot  contain  in  all  a  less  vertical  thickness  of 
pure  graphite  than  from  twenty  to  thirty  feet.  In  the 
adjoining  township  of  Lochabox'  Sir  W.  E.  Logan  notices 
a  band  from  twenty-five  to  thirty  feet  thick,  reticulated 
with  graphite  veins  to  such  an  extent  as  to  be  mined  with 
profit  for  the  mineral.  At  another  place  in  the  same  dis- 
trict a  bed  of  graphite  from  ten  to  twelve  feet  thick,  and 
yielding  20  per  cent,  of  the  pure  material,  is  worked. 
As  it  appears  in  the  excavation  made  by  the  quarrymen, 
it  resembled  a  bed  of  coal ;  and  a  block  from  this  bed, 
about  four  feet  thick,  was  a  prominent  object  in  the 
Canadian  department  of  the  Colonial  Exhibition  of  1886. 
When  it  is  considered  that  graphite  occurs  in  similar 
abundance  at  several  other  horizons,  in  bods  of  limestone 
which  have  been  ascertained  by  Sir  W.  E.  Logan  to  have 
an  aggregate  thickness  of  thirty-five  hundred  feet,  it  is 


*  Paper  by  the  author  on  Laurentian  Graphite,  "  Journal  of  London 
Geological  Society,"  1816. 


12 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


scarcely  an  exagger  m  to  maintain  that  the  quantity  of 
carbon  in  the  Lau  lan  is  equal  to  that  in  similar  areas 
of  the  Carboniferou.,  system.  It  is  also  to  be  observed 
that  an  immense  area  in  Canada  appears  to  be  occupied 
by  these  graphitic  and  Eozoon  limestones,  and  that  rich 
graphitic  deposits  exist  in  the  continuation  of  this  sys- 
tem in  the  State  of  New  York,  while  in  rocks  believed  to 
be  of  this  age  near  St.  John,  New  Brunswick,  there  is  a 
very  thick  bed  of  graphitic  limestone,  and  associated  with 
it  three  regular  beds  of  graphite,  having  an  aggregate 
thickness  of  about  five  feet.* 

It  may  fairly  be  assumed  that  in  the  present  world, 
and  in  those  geological  periods  with  whose  organic  re- 
mains we  are  more  familiar  than  with  those  of  the  Lau- 
rentian,  there  is  no  other  source  of  unoxidized  carbon  in 
rocks  than  that  furnished  by  organic  matter,  and  that 
this  has  obtained  its  carbon  in  all  cases,  in  the  first  in- 
stance, from  the  deoxidation  of  carbonic  acid  by  living 
plants.  No  other  source  of  carbon  can,  I  believe,  be 
imagined  in  the  Laurentian  period.  We  may,  however, 
suppose  either  that  the  graphitic  matter  of  the  Laurentian 
has  been  accumulated  in  beds  like  those  of  coal,  or  that 
it  has  consisted  of  diffused  bituminous  matter  similar  to 
that  in  more  modern  bituminous  shales  and  bituminous 
and  oil-bearing  limestones.  Tne  beds  of  graphite  near 
St.  John,  some  of  those  in  the  gneiss  at  Ticonderoga  in 
New  York,  and  at  Lochaber  and  Buckingham,  and  else- 
where in  Canada,  are  so  pure  and  regular  that  one  might 
fairly  compare  them  with  the  graphitic  coal  of  Rhode 
Island.  These  instances,  however,  are  exceptional,  and 
the  greater  part  of  the  disseminated  and  vein  graphite 
might  rather  be  likened  in  its  mode  of  occurrence  to  the 
bituminous  matter  in  bituminous  shales  and  limestones. 


*  Matthew  in  "  Quarterly  Journal  of  the  Geological  Society,"  vol. 
xxi.,  p.  423.     "Acadian  Geology,"  p.  662. 


Ml'  mt-uiMiaum.m:iii»n 


LAURENTIAN  AND   EARLY  PALAEOZOIC, 


13 


We  may  compare  the  disseminated  graphite  to  that 
which  we  find  in  those  districts  of  Canada  in  which  Silu- 
rian and  Devonian  bituminous  shales  and  limestones  have 
been  metamorphosed  and  converted  into  graphitic  rocks 
not  very  dissimilar  to  those  in  the  less  altered  portions  of 
the  Laurontian.*  In  like  manner  it  seems  probable  that 
the  numerous  reticulating  veins  of  graphite  may  have 
been  formed  by  the  segregation  of  bituminous  matter  into 
fissures  and  planes  of  least  resistance,  in  the  manner  in 
which  such  veins  occur  in  modern  bituminous  limestones 
and  shales.  Such  bituminous  veins  occur  in  the  Lower 
Carboniferous  limestone  and  shale  of  Dorchester  and 
Hillsborough,  New  Brunswick,  with  an  arrangement  very 
similar  to  that  of  the  veins  of  graphite  ;  and  in  the  Que- 
bec rocks  of  Point  Levi,  veins  attaining  to  a  thickness  of 
more  than  a  foot,  are  filled  with  a  coaly  matter  having  a 
transverse  columnar  structure,  and  regarded  by  Logan 
and  Hunt  as  an  altered  bitumen.  These  palaeozoic  analo- 
gies would  lead  us  to  infer  that  the  larger  part  of  the 
Laurentian  graphite  falls  under  the  second  class  of  de- 
posits above  mentioned,  and  that,  if  of  vegetable  origin, 
the  organic  matter  must  have  been  thoroughly  disin- 
tegrated and  bituminised  before  it  was  changed  into 
graphite.  This  would  also  give  a  probability  that  the 
vegetation  implied  was  aquatic,  or  at  least  that  it  was 
accumulated  under  water. 

Dr.  Hunt  has,  however,  observed  an  indication  of  ter- 
restrial vegetation,  or  at  least  of  subaerial  decay,  in  the 
great  beds  of  Laurentian  iron-ore.  These,  if  formed  in 
the  same  manner  as  more  modern  deposits  of  this  kind, 
would  imply  the  reducing  and  solvent  action  of  sub- 
stances produced  in  the  decay  of  plants.  In  this  case 
such  great  ore-beds  as  that  of  Hull,  on  the  Ottawa,  seventy 


*  Granby,  Melbourne,  Owl's  Head,  &c.,  "  Geology  of  Canada,"  1863, 
p.  699. 


rr 


14 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


feet  thick,  or  that  near  Newboroagh,  two  hundred  feet 
thick,*  must  represent  a  corresponding  quantity  of  vege- 
table matter  which  has  totally  disappeared.  It  may  be 
added  that  similar  demands  on  vegetable  matter  as  a 
deoxidising  agent  are  made  by  the  beds  and  veins  of 
metallic  sulphides  of  the  Laurentian,  though  some  of 
the  latter  are  no  doubt  of  later  date  than  the  Laurentian 
rocks  themselves. 

It  would  be  very  desirable  to  confirm  such  conclusions 
as  those  above  deduced  by  the  evidence  of  actual  micro- 
scopic structure.  It  is  to  be  observed,  however,  that 
when,  in  more  modern  sediments,  Algae  have  been  con- 
verted into  bituminous  matter,  we  cannot  ordinarily  ob- 
tain any  structural  evidence  of  the  origin  of  such  bitumen, 
and  in  the  graphitic  slates  and  limestones  derived  from 
the  metamorphosis  of  such  rocks  no  organic  structure 
remains.  It  is  true  that,  in  certain  bituminous  shales 
and  limestones  of  the  Silurian  system,  shreds  of  organic 
tissue  can  sometimes  be  detected,  and  in  some  cases,  as 
in  the  Lower  Silurian  limestone  of  the  La  Cloche  Mount- 
ains in  Canada,  the  pores  of  brachiopodous  shells  and 
the  cells  of  corals  have  been  penetrated  by  black  bitu- 
minous matter,  forming  what  may  be  regarded  as  natural 
injections,  sometimes  of  much  beauty.  In  correspondence 
with  this,  while  in  some  Laurentian  graphitic  rocks,  as, 
for  instance,  in  the  compact  graphite  of  Clarendon,  the 
carbon  presents  a  curdled  appearance  due  to  segregation, 
and  precisely  similar  to  that  of  the  bitumen  in  more 
modern  bituminous  rocks,  I  can  detect  in  the  graphitic 
limestones  occasional  fibrous  structures  which  may  be 
remains  of  plants,  and  in  some  specimens  vermicular 
lines,  which  I  believe  to  be  tubes  of  Eozoon  penetrated 
by  matter  once  bituminous,  but  now  in  the  state  of 
graphite. 


» «» 


Geology  of  Canada,"  1863. 


LAURENTIAN  AND  EARLY  PALJIOZOIC. 


15 


When  palaeozoic  land-plants  have  been  con  verted  into 
graphite,  they  sometimes  perfectly  retain  their  structure. 
Mineral  charcoal,  with  structure,  exists  in  the  graphitic 
coal  of  Rhode  Island.  The  fronds  of  ferns,  with  their 
minutest  veins  perfect,  are  preserved  in  the  Devonian 
shales  of  St.  John,  in  the  state  of  graphite ;  and  in  the 
same  formation  there  are  trunks  of  Conifers  {Dadoxylon 
Ouangondianum)  in  which  the  material  of  the  cell-walls 
has  been  converted  into  graphite,  while  their  cavities 
have  been  filled  with  calcareous  spar  and  quartz,  the 
finest  structures  being  preserved  quite  as  well  as  in  com- 
paratively unaltered  specimens  from  the  coal-formation.* 
No  structures  so  perfect  have  as  yet  been  detected  in  the 
Laurentian,  though  in  the  largest  of  the  three  graphitic 
beds  at  St.  John  there  appear  to  be  fibrous  structures, 
which  I  believe  may  indicate  the  existence  of  land-plants. 
This  graphite  is  composed  of  contorted  and  slickensided 
laminae,  much  like  those  of  some  bituminous  shales  and 
coarse  coals;  and  in  these  are  occasional  small  pyritous 
masses  which  show  hollow  carbonaceous  fibres,  in  some 
cases  presenting  obscure  indications  of  lateral  pores.  I 
regard  these  indications,  however,  as  uncertain ;  and  it  is 
not  as  yet  fully  ascertained  that  these  beds  at  St.  John 
are  on  the  same  geological  horizon  with  the  Lower  Lau- 
rentian of  Canada,  though  they  certainly  underlie  the 
Primordial  series  of  the  Acadian  group,  and  are'  sepa- 
rated from  it  by  beds  having  the  character  of  the  Hu- 
ronian. 

There  is  thus  no  absolute  impossibility  that  distinct 
organic  tissues  may  be  found  in  the  Laurentian  graphite, 
if  formed  from  land-plants,  more  especially  if  any  plants 
existed  at  that  time  having  true  woody  or  vascular  tissues ; 
but  it  cannot  with  certainty  be  affirmed  that  such  tissues 


*  "  Acadian  Geology,"  p.  535,     In  calcified  specimens  th§  structures 
remain  in  the  graphite  after  decalcification  by  an  acid. 


16 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


I'   i 


4il 


have  been  found.  It  is  possible,  however,  that  in  the 
Laurentian  period  the  vegetation  of  the  land  may  have 
consisted  wholly  of  cellular  plants,  as,  for  example, 
mosses  and  lichens ;  and  if  so,  there  would  be  compara- 
tively little  hope  of  the  distinct  preservation  of  their 
forms  or  tissues,  or  of  our  being  able  to  distinguish  the 
remains  of  land-plants  from  those  of  AlgaB. 

We  may  sum  up  these  facts  and  considerations  in  the 
following  statements :  First,  that  somewhat  obscure 
traces  of  organic  structure  can  be  detected  in  the  Lauren- 
tian graphite ;  secondly,  that  the  general  arrangement 
and  microscopic  structure  of  the  substance  corresponds 
with  that  of  the  carbonaceous  and  bituminous  matters  in 
marine  formations  of  more  modern  date  ;  thirdly,  that  if 
the  Laurentian  graphite  has  been  derived  from  vegetable 
matter,  it  has  only  undergone  a  metamorphosis  similar  in 
kind  to  that  which  organic  matter  in  metamorphosed 
sediments  of  later  age  has  experienced ;  fourthly,  that  the 
association  of  the  graphitic  matter  with  organic  lime- 
stone, beds  of  iron-ore,  and  metallic  sulphides  greatly 
strengthens  the  probability  of  its  vegetable  origin ;  fifthly, 
that  when  we  consider  the  immense  thickness  and  extent 
of  the  Eozoonal  and  graphitic  limestones  and  iron-ore 
deposits  of  the  Laurentian,  if  we  admit  the  organic  origin 
of  the  limestone  and  graphite,  we  must  be  prepared  to 
believe  that  the  life  of  that  early  period,  though  it  may 
have  existed  under  lov/  forms,  was  most  copiously  devel- 
oped, and  that  it  equalled,  perhaps  surpassed,  in  its  re- 
sults, in  the  way  of  geological  accumulation,  that  of  any 
subsequent  period. 

Many  years  ago,  at  the  meeting  of  the  American  As- 
sociation in  Albany,  the  writer  was  carrying  into  the 
room  of  the  Geological  Section  a  mass  of  fossil  wood  from 
the  Devonian  of  Gasp6,  when  he  met  the  late  Professor 
Agassiz,  and  remarked  that  the  specimen  was  the  re- 
mains   of   a   Devonian   tree  contemporaneous  with  his 


LAURENTIAN  AND  EARLY  PALEOZOIC. 


17 


1 


fishes  of  that  age.  "  How  I  wish  I  could  sit  under  its 
shade  ! "  was  the  smiling  reply  of  the  great  zoologist ;  and 
when  we  think  of  the  great  accumulations  of  Laurentian 
carbon,  and  that  we  are  entirely  ignorant  of  the  forms 
and  structures  of  the  vegetation  which  produced  it.  we 
can  scarcely  suppress  a  feeling  of  disappointment.  Some 
things,  however,  we  can  safely  infer  from  the  facts  that 
are  known,  and  these  it  may  be  well  to  mention. 

The  climate  and  atmosphere  of  the  Laurentian  may 
have  been  well  adapted  for  the  sustenance  of  vegetable 
life.  We  can  scarcely  doubt  that  the  internal  heat  of  the 
earth  still  warmed  the  waters  of  the  sea,  and  these  warm 
waters  must  have  diffused  great  quantities  of  mists  and 
vapours  over  the  land,  giving  a  moist  and  equable  if  not  a 
very  clear  atmosphere.  The  vast  quantities  of  carbon  di- 
oxide afterwards  sealed  up  in  limestones  and  carbonaceous 
beds  must  also  have  still  floated  in  the  atmosphere  and 
must  have  supplied  abundance  of  the  carbon,  which  con- 
stitutes the  largest  ingredient  in  vegetable  tissues.  Under 
these  circumstances  the  whole  world  must  have  resembled 
a  damp,  warm  greenhouse,  and  plants  loving  such  an  at- 
mosphere could  have  grown  luxuriantly.  In  these  cir- 
cumstances the  lower  forms  of  aquatic  vegetation  and 
those  that  love  damp,  warm  air  and  wet  soil  would  have 
been  at  home. 

If  we  ask  more  particularly  what  kinds  of  plants 
might  be  expected  to  be  introduced  in  such  circumstances, 
we  may  obtain  some  information  from  the  vegetation  of 
the  succeeding  Palaeozoic  age,  when  such  conditions  still 
continued  to  a  modified  extent.  In  this  period  the  club- 
mosses,  ferns,  and  mare's-tails  engrossed  the  world  and 
grew  to  sizes  and  attained  degrees  of  complexity  of  struc- 
ture not  known  in  modern  times.  In  the  previous  Lau- 
rentian age  something  similar  may  have  happened  to 
AlgaB,  to  Fungi,  to  Lichens,  to  Liverworts,  and  Mosses. 
The  AlgsB  may  have  attained  to  gigantic  dimensions,  and 


18 


THE  GEOLOGICAL  HISTORY  OF  PLANTa 


may  have  even  ascended  out  of  the  water  in  some  of  their 
forms.  These  comparatively  simple  cellular  and  tubular 
structures,  now  degraded  to  the  humble  position  of  flat 
lichens  or  soft  or  corky  fungi,  or  slender  cellular  mosses, 
may  have  been  so  strengthened  and  modified  as  to  con- 
stitute forest-trees.  This  would  be  quite  in  harmony  with 
what  is  observed  in  the  development  of  other  plants  in 
primitive  geological  times  ;  and  a  little  later  in  this  his- 
tory we  shall  see  that  there  is  evidence  in  the  flora  of  the 
Silurian  of  a  survival  of  such  forms. 

It  may  be  that  no  geologist  or  botanist  will  ever  be 
able  to  realise  these  dreams  of  the  past.  But,  on  the 
other  hand,  it  is  quite  possible  that  some  fortunate  chance 
may  have  somewhere  preserved  specimens  of  Laurentian 
plants  showing  their  structure. 

In  any  case  we  have  here  presented  to  us  the  strange 
and  startling  fact  that  the  remarkable  arrangement  of 
protoplasmic  matter  and  chlorophyll,  which  enables  the 
vegetable  cell  to  perform,  with  the  aid  of  solar  light,  the 
miracle  of  decomposing  carbon  dioxide  and  water,  and 
forming  ^rith  them  woody  and  corky  tissues,  had  already 
been  introduced  upon  the  earth.  It  has  been  well  said 
that  no  amount  of  study  of  inorganic  nature  would  ever 
have  enabled  any  one  to  anticipate  the  possibility  of  the 
construction  of  an  apparatus  having  the  chemical  powers 
of  the  living  vegetable  cell.  Yet  this  most  marvellous 
structure  seems  to  have  been  introduced  in  the  full  pleni- 
tude of  its  powers  in  the  Laurentian  age. 

Whether  this  early  Laurentian  vegetation  was  the 
means  of  sustaining  any  animal  life  other  than  marine 
Protozoa,  we  do  not  know.  It  may  have  existed  for  its 
own  sake  alone,  or  merely  as  a  purifier  of  the  atmosphere, 
in  preparation  for  the  future  introduction  of  land-ani- 
mals. The  fact  that  there  have  existed,  even  in  modern 
times,  oceanic  islands  rich  in  vegetation,  yet  untenanted 
by  the  higher  forms  of  animal  life,  prepares  us  to  believe 


LAURENTIAN   AKD  EARLY   PALJiOZOiC. 


19 


that  such  conditions  may  have  been  general  or  universal 
in  the  primeval  times  we  are  here  considering. 

If  we  ask  to  what  extent  the  carbon  extracted  from 
the  atmosphere  and  stored  up  in  the  earth  has  been, 
or  is  likely  to  be,  useful  to  man,  the  answer  must  be 
that  it  is  not  in  a  state  to  enable  it  to  be  used  as  min- 
eral fuel.  It  has,  however,  important  uses  in  the  arts, 
though  at  present  the  supply  seems  rather  in  excess  of 
the  demand,  and  it  may  well  be  that  there  are  uses  of 
graphite  still  undiscovered,  and  to  which  it  will  yet  be 
applied. 

Finally,  it  is  deserving  of  notice  that,  if  Lauren  tian 
graphite  indicates  vegetable  life,  it  indicates  this  in  vast 
profusion.  That  incalculable  quantities  of  vegetable 
matter  have  been  oxidised  and  have  disappeared  we  may 
believe  on  the  evidence  of  the  vast  beds  of  iron-ore  ;  and, 
in  regard  to  that  preserved  as  graphite,  it  is  certain  that 
every  inch  of  that  mineral  must  indicate  many  feet  of 
crude  vegetable  matter. 

It  is  remarkable  that,  in  ascending  from  the  Lauren- 
tian,  we  do  not  at  first  appear  to  advance  in  evidences 
of  plant-life.  The  Huronian  age,  which  succeeded  the 
Laurentian,  seems  to  have  been  a  disturbed  and  unquiet 
time,  and,  except  in  certain  bands  of  iron-ore  and  some 
dark  slates  coloured  with  carbonaceous  matter,  we  find  in 
it  no  evidence  of  vegetation.  In  the  Cambrian  a  great 
subsidence  of  our  continents  began,  which  went  on, 
though  with  local  intermissions  and  reversals,  all  through 
the  Siluro-Cambrian  or  Ordovician  time.  These  times 
were,  for  this  reason,  remarkable  for  the  great  abundance 
and  increase  of  marine  animals  rather  than  of  land-plants. 
Still,  there  are  some  traces  of  land  vegetation,  and  we  may 
sketch  first  the  facts  of  this  kind  which  are  known,  and 
then  advert  to  some  points  relating  to  the  earlier  Algae, 
or  sea-weeds. 

An  eminent  Swedish  geologist,  Linnarsson,  has  de- 


20 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


I . 


■ 


scribed,  under  the  name  of  Eophyton,  certain  impressione 
on  old  Cambrian  rocks  in  Sweden,  and  which  certainly 
present  very  plant-like  forms.  They  want,  however,  any 
trace  of  carbonaceous  matter,  and  seem  rather  to  be 
grooves  or  marks  cut  in  clay  by  the  limbs  oi  tails  of  some 
aquatic  animal,  and  afterwards  filled  up  and  preserved  by 
succeeding  deposits.  After  examining  large  scries  of 
these  specimens  from  Sweden,  and  from  rocks  of  similar 
age  in  Canada,  I  confess  that  I  have  no  faith  in  their 
vegetable  nature. 

The  oldest  plants  known  to  me,  and  likely  to  have 
been  of  higher  grade  than  Algaa,  are  specimens  kindly 
presented  to  me  by  Dr.  Alleync  Nicholson,  of  Aberdeen, 
and  which  he  had  named  Buthotrephis  Jlarknessii*  and 
B.  radiata.  They  are  from  the  Skiddaw  rocks  of  Cum- 
berland. On  examining  these  specimens,  and  others 
subsequently  collected  in  the  same  locality  by  Dr.  G.  M. 
Dawson,  while  convinced  by  their  form  and  carbonaceous 
chaiacter  that  they  are  really  plants,  I  am  inclined  to  re- 
fer them  not  to  Algse,  but  probably  to  Rhizocarps.  They 
consist  of  slender  branching  stems,  with  whorls  of  elongate 
and  pointed  leaves,  resembling  the  genus  Annularia  of 
the  coal  formation.  I  am  inclined  to  believe  that  both 
of  Nicholson's  species  are  parts  of  one  plant,  and  for 
this  I  have  proposed  the  generic  name  Protannularia 
(Fig.  1).  Somewhat  higher  in  the  Siluro-Cambrian,  in 
the  Cincinnati  group  of  America,  Lcsquercux  has  found 
some  minute  radiated  leaves,  referred  by  him  to  the  genus 
Sphenophyllum,]  which  is  also  allied  to  Rhizocarps.  Still 
more  remarkable  is  the  discovery  in  the  same  beds  of  a 
stem  with  rhombic  areoles  or  leaf-bases,  to  which  the 
name  Protostigma  has  been  given.  J     If  a  plant,  this  may 


*  "  Geological  Magazine,"  1869. 

f  See  figure  in  next  chapter. 

\  Frotostigma  siffillarioidcs,  Lcsqucreux. 


r--t_ 


r-Tn 


i^KPMtl^h^tHmiralt 


LAUREXTIAN   AND  EARLY   PALiEOZOIC. 


21 


have  been  allied  to  the  club-mosses.     This  seems  to  bo 

all  that  we  at  present  know  of  land-vegetation  in  the 

Siluro-Cambrian.    So  far  as  the  remains  go,  they  indicate 

the  presence  of  the 

families  of  Rhizo- 

carps  and  of  Lyco- 

pods. 

If  we  ascend 
into  the  Uj)per  Si- 
lurian, or  Siluri- 
an proper,  the  evi- 
dences of  land  veg- 
etation somewhat 
increase.  In  1859  I 
described.,  in  "The 
Journal  of  the  Geo- 
logical Society,"  of 
London,  a  remark- 
able tree  from  the 
Lower  Erian  of 
Guspe,  under  the 
name  Frotoiaxites, 
but  for  which  I 
now  prefer  the 
name  Nematophy- 
ton.  When  in  Lon- 
don, in  1870,  I  obtained  permission  to  exami  e  cer- 
tain specimens  of  spore-cases  or  seeds  from  the  Upper 
Ludlow  (Silurian)  formation  of  England,  and  which 
h'ld  been  described  by  Sir  Joseph  Hooker  under  the 
name  Pachytheca.  In  the  same  slabs  with  these  I 
found  fragments  of  fossil  wood  identical  with  those 
of  the  Gaspe  plant.  Still  later  I  recognised  similar 
fragments  associated  also  with  Pachytheca  in  the  Silu- 
rian of  Cape  Bon  Ami,  New  Brunswick.     Lastly,  Dr. 

Hicks    has  discovered    similar   wood,  and   also  similar 
4 


Fio.  1. — Protanntilaria  Ilarknesni  (Nichol- 
Bon),  a  probable  Rhizocarp  of  the  Ordo- 
vician  period. 


22 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


fruits,  in  the  Denbighshire  grits,  at  the  base  of  the  Si- 
lurian.* 

II 


Fio.  2. — Nematophyton  Logani  (magnified).    Vertical  section. 

From  comparison  of  this  singular  wood,  the  structure 
of  which  is  represented  in  Figs.  2,  3,  4,  with  the  debris 


FiQ.  8. — Nematophyton  Logani  (magnified).    Horizontal  section,  showing 
part  of  one  of  the  radial  spaces,  with  tubes  passing  into  it. 

of  fossil  taxine  woods,  mineralised  after  long  maceration 
in  water,  I  was  inclined  to  regard  Prototaxitett,  or,  as  I 


*  "Journal  of  the  Geological  Society,"  August,  1881. 


LAUREXTIAN  AND  EARLY   PALJIOZOIO. 


23 


have  more  recently  named  it,  Nematophyton,  as  a  prime- 
val gymnosperm  allied  to  those  trees  which  linger  had 
described  from  the  Erian  of  Thuringia,  under  the  name 
Aporoxylon*  Later  examples  of  more  lax  tissues  from 
branches  or  young  stems,  and  the  elaborate  examinations 
kindly  undertaken  for  me  by  Professor  Penhallow  and 


Fio.  4. — Nematophyton  Logani  (magnified).     Restoration. t 

referred  to  in  a  note  to  this  chapter,  have  induced  me  to 
modify  this  view,  and  to  hold  that  the  tissues  of  these 
singular  trees,  which  seem  to  have  existed  from  the  be- 

*  "  Palacontologic  des  Thuringcr  Waldes,"  1856. 
f  Fig.s.  2,  3,  and  4  arc  drawn  from  nature  by  Prof.  Ponhallow,  of 
McGill  College. 


H 


24 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


t 


ginning  of  the  Silurian  age  and  to  have  finally  disap- 
peared in  the  early  Erian,  are  altogether  distinct  from 
any  form  of  vegetation  hitherto  known,  and  are  possibly 
survivors  of  that  prototypal  flora  to  which  I  have  already 
referred.  They  are  trees  of  large  size,  with  a  coaly  bark 
and  large  spreading  roots,  having  the  surface  of  the  stem 
smooth  or  irregularly  ribbed,  but  with  a  nodose  or  jointed 
appearance.  Internally,  they  show  a  tissue  of  long,  cylin- 
drical tubes,  traversed  by  a  complex  network  of  horizontal 
tubes  thinner  walled  and  of  smaller  size.  The  tubes  are 
arranged  in  concentric  zones,  which,  if  annual  rings,  would 
in  some  specimens  indicate  an  age  of  one  hundred  and 
fifty  years.  There  are  also  radiating  spaces,  which  I  was 
at  first  disposed  to  regard  as  true  medullary  rays, «  ;  which 
at  least  indicate  a  radiating  arrangement  of  the  tissue. 
They  now  seem  to  be  spaces  extending  from  the  centre 
towards  the  circumference  of  the  stem,  and  to  have  con- 
tained bundles  of  tubes  gathered  from  the  general  tissue 
and  extending  outward  perhaps  to  organs  or  appendages 
on  the  surface.  Carruthers  has  suggested  a  resemblance 
to  Algae,  and  has  ev^en  proposed  to  change  the  name  to 
Nematophycus,  or  "thread -sea- weed";  but  the  resem- 
blance is  by  no  means  clear,  and  it  would  be  quite  as  rea- 
sonable to  compare  the  tissue  to  that  of  some  Fungi  or  Li- 
chens, or  even  to  suppose  that  a  plant  composed  of  cylin- 
drical tubes  has  been  penetrated  by  the  mycelium  or  spawn 
of  a  dry-rot  fungus.  But  the  tissues  are  too  constant  and 
too  manifestly  connected  with  each  other  to  justify  this 
last  supposition.  Th  it  the  plant  grew  on  land  I  cannot 
doubt,  from  its  mode  of  occurrence ;  that  it  was  of  dura- 
ble and  resisting  character  is  shown  by  its  state  of  preser- 
vation ;  and  the  structure  of  the  seeds  called  Pachytheca, 
with  their  constant  association  with  these  trees,  give  coun- 
tenance to  the  belief  that  they  are  the  rruit  of  Nema- 
tophyton.  Of  the  foliage  or  fronds  of  these  strange 
plants  we  unfortunately  know  nothing.     They  seem,  how- 


LAURENTIAN  AND  EARLY  PALEOZOIC. 


25 


ever,  to  realise  the  idea  of  arboreal  plants  having  struct- 
ures akin  to  those  of  thallophytes,  but  with  seeds  so 
large  and  complex  that  they  can  scarcely  be  regarded  as 
mere  spores.  They  should  perhaps  constitute  a  separate 
class  or  order  to  which  the  name  NematodendrecB  may 
be  given,  and  of  which  Nematophyton  will  constitute  one 
genus  and  Aporoxylon  of  linger  another.* 

Another  question  arises  as  to  the  possible  relation  of 
these  plants  to  other  trees  known  by  their  external  forms. 
The  Protostigma  of  Lesquereux  has  already  been  referred 
to,  and  Claypole  has  described  a  tree  from  the  Clinton 
group  of  the  United  States,  with  large  ovate  leaf-bases,  to 
which  he  has  given  the  name  Glyptodendron.\  If  the 
markings  on  these  plants  are  really  leaf-bases,  they  can 
scarcely  have  been  connected  with  Nematophyton^  because 
that  tree  shows  no  such  surface-markings,  though,  as  we 
have  seen,  it  had  bundles  of  tubes  passing  diagonally  to 
the  surface.  These  plants  were  more  probably  trees  with 
an  axis  of  barred  vessels  and  thick,  cellular  bark,  like  the 
Lepidodendron  of  later  periods,  to  be  noticed  in  the  sequel. 
Dr.  Hicks  has  also  described  from  the  same  series  of  beds 
which  afforded  the  fragments  of  Nematophyton  oertairj 
carbonised  dichotomous  stems,  which  he  has  named  Bsr~ 
wynia.  It  is  just  possible  that  these  plants  may  have 
belonged  to  the  Nematodendreae.  The  thick  and  dense 
coaly  matter  which  they  show  resembles  the  bark  of  these 
trees,  the  longitudinal  striation  in  some  of  them  may 
represent  the  fibrous  structure,  and  the  lateral  projections 
which  have  been  compared  to  leaves  or  leaf-bases  may 
correspond  with  the  superficial  eminences  of  Nematophy- 
ton, and  the  spirally  arranged  pimctnres  which  it  pi.<^jws 
on  its  surface.     In  this  case  I  stiojld  hi  disposed  to  ^g- 


*  See  report  by  the  author  on  "Brian  Flora  of  Canada,"  1871  and 
1882,  for  full  description  of  these  fossils. 
\  "  American  Journal  of  Science,"  1878. 


26 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


gard  the  supposed  stigmaria-like  roots  as  really  ^fems, 
and  the  supposed  rootlets  as  short,  spine-like  ru*  ent- 
arj  leaves.  All  such  comparisons  must,  however,  m  the 
mean  time  be  regarded  as  conjectural.  We  seem,  how- 
ever, to  have  here  a  type  of  tree  very  dissimilar  to  any 
even  of  the  later  Palaeozoic  age,  which  existed  through- 
out the  Silurian,  and  probably  further  back,  which  ceased 
to  exist  early  in  the  Erian  age,  and  before  the  appearance 
of  tWfe  ordinary  coniferou  and  lepidodendroid  trees. 
May  it  not  have  been  a  survivor  of  an  old  arboreal  flora 
extending  back  even  to  the  Laurentian  itself  ? 

Multitudes  of  markings  occurring  on  the  surfaces  of 
the  older  rocks  have  been  referred  to  the  Algae  or  sea- 
weeds, and  indeed  this  group  has  been  a  sort  of  refuge  for 
the  destitute  to  which  palaeontologists  have  been  accus- 
tomed to  refer  any  anomalous  or  inexplicable  form  which, 
while  probably  organic,  could  not  be  definitely  referred  to 
the  animal  kingdom.  There  can  be  no  question  that  some 
of  these  are  truly  marine  plants  ;  and  that  plants  of  this 
kind  occur  in  formations  older  than  those  in  which  we  first 
find  land-plants,  and  that  they  have  continued  to  inhabit 
the  sea  down  to  the  present  time.  It  is  also  true  that  the 
oldest  of  these  Algae  closely  resemble  in  form  plants  of 
this  kind  still  existing ;  and,  since  their  simple  cellular 
structures  and  soft  tissues  are  scarcely  ever  preserved, 
their  general  forms  are  all  that  we  can  know,  so  that  their 
exact  resemblance  to  or  difference  from  modern  types  can 
rarely  be  determined.  For  the  same  reasons  it  has  proved 
difficult  clearly  to  distinguish  them  from  mere  inorganic 
markings  or  the  traces  of  animals,  and  the  greatest  di- 
vergence of  ojiinion  has  occurred  in  recent  times  on  these 
subjects,  as  any  one  can  readily  understand  who  consults 
the  voluminous  and  well-illustrated  memoirs  of  Nathorst, 
Williamson,  Saporta,  and  Delgado. 

The  author  of  this  work  has  given  much  attention  to 
these  remains,  and  has  not  been  disposed  to  claim  for  the 


LAURENTIAN  AND   EARLY  PALEOZOIC. 


27 


vegetable  kingdom  so  many  of  them  as  some  of  his  con- 
temporaries.* The  considerations  which  seem  most  im- 
portant in  making  such  distinctions  are  the  following : 
1.  The  presence  or  absence  of  carbonaceous  matter. 
True  Algae  not  infrequently  present  at  least  a  thin  film  of 
carbon  representing  their  organic  matter,  and  this  is  the 
more  likely  to  occur  in  their  case,  as  organic  matters 
buried  in  marine  deposits  and  not  exposed  to  atmospheric 
oxidation  are  very  likely  to  be  preserved.  2.  In  the 
absence  of  organic  matter,  the  staining  of  the  containing 
rock,  the  disappearance  or  deoxidation  of  its  ferruginous 
colouring  matter,  or  the  presence  of  iron  pyrite  may  indi- 
cate the  removal  of  organic  matter  by  decay.  3.  When 
organic  matter  and  indications  of  it  are  altogether  absent, 
and  form  alone  remains,  we  have  to  distinguish  from  Algae, 
trails  and  burrows  similar  to  those  of  aquatic  animals, 
casts  of  shrinkage-cracks,  water-marks,  and  rill-marks 
widely  diffused  over  the  surfaces  of  beds.  4.  Markings 
depressed  on  the  upper  surfaces  of  beds,  and  filled  with 
the  material  of  the  succeeding  layer,  are  usually  mere  im- 
pressions. The  cases  of  possible  exceptions  to  this  are 
very  rare.  On  the  contrary,  there  are  not  infrequently 
forms  in  relief  on  the  surfaces  of  rocks  which  are  not 
Algae,  but  may  be  shallow  burrows  arched  upward  on  top, 
or  castings  of  worms  thrown  up  upon  the  surface.  Some- 
times, however,  they  may  have  been  left  by  denudation 
of  the  surrounding  material,  just  as  footprints  on  dry 
snow  remain  in  relief  after  the  surrounding  loose  material 
has  been  drifted  away  by  the  wind ;  the  portion  consoli- 
dated by  pressure  being  better  able  to  resist  the  denuding 
agency. 

The  footprints  from  the  Potsdam  sandstone  in  Can- 
ada, for  which  the  name  Protichnites  was  proposed  by 


*  "  Impressions  and   Footprints  of  Aquatic  Animals,"  "  American 
Journal  of  Science,"  1873. 


28 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


I 


Owen,  and  which  were  by  him  referred  to  crustaceans 
probably  resembling  Limulus,  were  shown  by  the  writer, 

in  1862,*  to  correspond 
precisely  with  those  of  the 
American  Limulus  {Poly- 
phemus Occidentalis)  (Fig. 
5).  I  proved  by  experi- 
ment with  the  modern  ani- 
mal that  the  recurring  se- 
ries of  groups  of  markings 
were  produced  by  the  toes 
of  the  large  posterior  tho- 
racic feet,  the  irregular 
scratches  seen  in  Protich- 
nites  lineatus  by  the  ordi- 
nary feet,  and  the  central  furrow  by  the  tail.  It  was  also 
shown  that  when  the  Limulus  uses  its  swimming-feet  it 
produces  impressions  of  the  character  of  those  named 


Fio.   5. — Trail  of  a  modem  king- 
crab,  to  illustrate  imitations  of 
Jlants  Hometiincs  named  Bilo- 
Ues. 


Fig.  6. — Trail  of  Oarboniferous  crustacean  (Eusichnites  Acadicua)^  Nova 
Scotia,  to  illustrate  supposed  Alga3. 


i      ! 


*  "  Canadian  Naturalist,"  vol.  vii. 


LAURENTIAN  AND  EARLY   PALEOZOIC. 


29 


ClimacticJiniteSy  from  the  same  beds  which  afford  Pro- 
ticlinites.    The  principal  difference  between  Protichnites 
and  their  modern  representatives  is  that  the  latter  have 
two  lateral  furrows 
produced    by    the 
sides  of   the   cara- 
pace,     which     are 
wanting  in  the  for- 
mer. 

I  subsequently 
applied  the  same 
explanation  to  sev- 
eral other  ancient 
forms  now  known 
under  the  gener- 
al name  Bilobites 
(Figs.  6  and  7).* 

The  tubercu- 
lated  impressions 
known  as  Phyma- 
toderma  and  Caul- 

erpites  may,  as  Zeil-     Yiq.  n,—Rmnphym%  {Rusichmtes)  Ormvillen- 

ler   has    shown,    be  **X  ^^  ammal  burrow  of  the  Siluro-Cam- 

,       ,        ,,        ,  brian,  probably  of  a  crustacean,    a,  Track 

made  by  the  bur-  connected  with  it. 
rowing  of  the  mole- 
cricket,  and  fine  examples  occurring  in  the  Clinton  forma- 
tion of  Canada  are  probably  the  work  of  Crustacea.  It  is 
probable,  however,  that  some  of  the  later  forms  referred 
to  these  genera  are  really  Algae  related  to  Caulerpa,  or 
even  branches  of  Conifers  of  the  genus  Brachyphyllum. 

Nereites  and  Planulitcs  are  tracks  and  burrows  of 
worms,  wif  .  or  without  marks  of  setae,  and  some  of  the 


*  The  name  Bilobiies  was  originally  proposed  by  Do  Kay  for  a  bivalve 
shell  {Conocardium).  Its  application  to  supposed  Algfc  was  an  error, 
but  this  is  of  the  less  consequence,  as  these  are  not  true  plants  but  only 
animal  trails. 


ii 


H 


ii     / . 


y  ! 

V  I 


: 

! 

1 

0 


30 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


markings  referred   to  ochorda,   Palceophycus,  and 

ScoUthus  have  their  ,  here.     Many  examples  highly 

illustrative  of  the  m         j  of  formation  of  the  impressions 
are  afforded  by  Canaaian  rocks  (Fig.  8). 

Branching  forois  referred  to  Licrophycus  of  Billings, 
and  some  of  those  referred  to  Butliotrephis,  Hall,  as  well 

as  radiating  markings 
referable  to  Scotolithus^ 
Oyropliyllites,  and  As- 
terophycus,  are  ex- 
plained by  the  branch- 
ing burrows  of  worms 
illustrated  by  Nathorst 
and  the  author.  As- 
tropoUthon,  a  singular 
radiating  marking  of 
the  Canadian  Cambri- 
an,* seems  to  be  some- 
thing organic,  but  of 
what  nature  is  uncer- 
tain (Fig.  9). 

Rhahdichnites  and 
EopTiyton  belong  to  im- 
pressions explicable  by 
the  trails  of  drifting 
sea-weeds,  the  tail-markings  of  Crustacea,  and  the  ruts 
ploughed  by  bivalve  mollusks,  and  occurring  in  the  Silu- 
rian, Erian,  and  Carboniferous  rocks,  f  Among  these  are 
the  singular  bilobate  forms  described  as  Rusophycus  by 
Hall,  and  which  are  probably  burrows  or  resting-places 
of  crustaceans.  The  tracks  of  such  animals,  when  walk- 
ing, are  the  jointed  impressions  known  as  Arthrophycus 
and  CruBiana.     I  have  shown  by  the  mode  of  occurrence 

*  Supplement  to  "  Acadian  Geology." 
t  "  Canadian  Naturalist,"  1864. 


f  lo.  8. — Palmophycua  Beverlyenns  (Bill- 
ings), a  supposed  Cambrian  Fucoid, 
but  probably  an  animal  trail. 


LAURENTIAN   AND  EARLY   PALAEOZOIC. 


81 


of  these,  and  Nathorst  has  confirmed  this  conclusion  by 
elaborate  experiments  on  living  animals,  that  these  forms 
are  really  trails  impressed  on  soft 
sediments  by  animals  and  mostly 
by  crustaceans. 

I  agree  with  Dr.  Williamson  * 
in  believing  that .  all  or  nearly  all 
the  forms  referred  to  Crossochorda 
of  Schimper  are  really  animal  im- 
pressions p'lied  to  Nereites,  and  due 
either  to  worms  or,  as  Nathorst  has 
shown  to  be  possible,  to  small  crus- 
taceans. Many  impressions  of  this 
kind  occur  in  the  Silurian  beds  of 
the  Clinton  series  in  Canada  and 
New  York,  and  are  undoubtedly 
mere  markings. 

It  is  worthy  of  note  that  these 
markings  strikingly  resemble  the  so- 
called  Eophyton,  described  by  Torell 
from  the  Primordial  of  Sweden,  and 
by  Billings  from  that  of  Newfound- 
land ;  and  which  also  occur  abun- 
dantly in  the  Primordial  of  New 
Brunswick.  After  examining  a  se- 
ries of  these  markings  from  Sweden 
shown  to  me  by  Mr.  Carruthers  in 
London,  and  also  specimens  from  Newfoundland  and 
a  large  number  in  situ  at  St.  John,  I  am  convinced 
that  they  cannot  be  plants,  but  must  be  markings  of 
the  nature  of  Rhahdichnites.  This  conclusion  is  based 
on  the  absence  of  carbonaceous  matter,  the  intimate 
union  of  the  markings  with  the  surface  of  the  stone, 


Fio.  9.  —  AdropoUthon 
Jlindii,  an  organism 
of  the  Lower  Cain- 
brittn  of  Nova  Scotia, 
possibly  vegetable. 


*  "  Tracks  from  Yoredale  Rocks,"  "  Manchester  Literary  and  Philo- 
sophical Society,"  188«. 


82 


THE  QEOLOGICAI.  HISTORY  OF  PLANTS. 


their  indefinite  forms,  their  want  of  nodes  or  append- 
ages, and  their  marliings  being  always  of  such  a  na- 
ture as  could  be  produced  by  scratches  of  a  sharp 
instrument.  Since,  however,  fishes  are  yet  unknown  in 
beds  of  this  age,  they  may  possibly  be  referred  to  the 
feet  or  spinous  tails  of  swimming  crustaceans.  Salter 
has  already  suggested  this  origin  for  some  scratchc  of 
somewhat  different  form  found  in  the  Primordial  of 
Great  Britain.  He  supposed  them  to  have  been  the 
work  of  species  of  Hymenocaris.  These  marks  may, 
however,  indicate  the  existence  of  some  free-swim- 
ming animals  of  the  Primordial  seas  as  yet  unknown 
to  us. 

Three  other  suggestions  merit  consideration  in  this 
connection.  One  is  that  Algas  and  also  land-plants,  drift- 
ing with  tides  or  currents,  often  make  the  most  remark- 
able and  fantastic  trails.  A  marking  of  this  kind  has 
been  observed  by  Dr.  G.  M.  Dawson  to  be  produced  by 
a  drifted  Laminaria,  and  in  complexity  it  resembled  the 
extraordinary  ^nigmichnus  multiformis  of  Hitchcock 
from  the  Connecticut  sandstones.  Much  more  simple 
markings  of  this  kind  would  suffice  to  give  species  of 
Eophyton.  Another  is  furnished  by  a  fact  stated  to  the 
author  by  Prof.  Morse,  namely,  that  Lingulse,  when  dis- 
lodged from  their  burrows,  trail  themselves  over  the 
bottom  like  worms,  by  means  of  their  cirri.  Colonies  of 
these  creatures,  so  abundant  in  the  Primordial,  may, 
when  obliged  to  remove,  have  covered  the  surfaces  of 
beds  of  mud  with  vermicular  markings.  The  third  is 
that  the  Rhabdichnite-markings  resemble  some  of  the 
grooves  in  Silurian  rocks  which  have  been  referred  to 
trails  of  Gasteropods,  as,  for  instance,  those  from  the 
Clinton  group,  described  by  Hall. 

Another  kind  of  markings  not  even  organic,  but  alto- 
gether depending  on  physical  causes,  are  the  beautiful 
branching  rill-marks  produced  by  the  oozing  of  water 


LAURENTIAN   AND  EARLY   PALiEOZOIO. 


33 


out  of  mud  and  sand-banks  left  by  the  tide,  and  which 
sometimes  cover  groat  surfaces  with  the  most  elaborate 
tracery,  on  the  modern  tidal  shores  as  well  as  in  some  of 
the  most  ancient  rocks.  Dendrophycus*  oi  Lesquereux 
seems  to  be  an  example  of  rill-mark,  as  well  as  Aristophy- 
cus,  Clwphycus,  and  Zygophycus,  of  Miller  and  Dyer, 
from  the  Lower  Silurian. 

Rill-marks  occur  in  very  old  rocks,  f  but  are  perhaps 
most  beautifully  preserved  in  the  Carboniferous  shales 
and  argillaceous  sandstones,  and 
even  more  elaborately  on  the  mod- 
ern mud  -  banks  of  the  Bay  of 
Fundy.J  Some  of  these  simulate 
ferns  and  fronds  of  Laminaria3, 
and  others  resemble  roots,  fucoids 
allied  to  Buthotrephis,  or  the  ra- 
diating worm-burrows  already  re- 
ferred to  (Fig.  10). 

Shrinkage-cracks  are  also  abun- 
dant in  some  of  the  Carboniferous 
beds,  and  are  sometimes  accom- 
panied with  impressions  of  rain- 
drops. When  finely  reticulated 
they  might  be  mistaken  for  the 
venation  of  leaves,  and,  when 
complicated  with  little  rill-marks 
tributary  to  their  sides,  they  pre- 
cisely resemble  the  Dictyolites  of 
Hall  from  the  Medina  sandstone 
(Fig.  11). 

An  entirely  different  kind  of  shrinkage-crack  is  that 
which  occurs  in  certain  carbonised  and  flattened  plants. 


Fig.  10. — Carboniferous  rill- 
mark  (Nova  Scotia),  re- 
duced, to  illubtrute  pre- 
tended Alg8B. 


*  "  Coal  Flora  of  Pennsylvania,"  vol.  iii,,  Plate  88, 
\  "Journal  of  the  Geological  Society,"  vol.  xii.,  p.  251. 
X  "  Acadian  Geology,"  2d  ed.,  p.  26. 
5 


I  H    I. 


U^ 


T 


34 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


and  which  sometimes  communicates  to  them  a  marvellous 
resemblance  to  the  netted  under  surface  of  an  exogenous 
leaf.  Flattened  stems  of  plants  and  layers  of  cortical 
matter,  when  carbonised,  shrink  in  such  a  manner  as  to 
produce  minute  reticulated  cracks.  These  become  filled 
with  mineral  matter  before  the  coaly  substance  has  been 
completely  consolidated.  A  further  compression  occurs, 
causing  the  coaly  substance  to  collapse,  leaving  the  little 
veins  of  harder  mineral  matter  projecting.  These  im- 
press their  form  upon  the  clay  or  shale  above  and  below, 
and  thus  when  the  mass  is  broken  open  we  have  a  car- 
bonaceous film  or  thin  layer  covered  with  a  network  of 

raised  lines,  and 
corresponding  mi- 
nute depressed 
lines  on  the  shale 
in  contact  with  it. 
The  reticulations 
are  generally  ir- 
regular, but  some- 
times they  very 
closely  resemble 
the  veins  of  a  re- 
ticulately  veined 
leaf.  One  of  the 
most  curious  speci- 
mens in  my  pos- 
session was  collect- 
ed by  Mr.  Elder 
in  the  Lower  Car- 
boniferous of  Ilorton  Bluff.  The  little  veins  which  form 
the  projecting  network  are  in  this  case  white  calcite  ;  but 
at  the  surface  their  projecting  edges  are  blackened  with 
a  carbonaceous  film. 

SUchensided  bodies^  resembling  the  fossil  fruits  de- 
scribed by  Geinitz  as  Oulielmites,  and  the  objects  believed 


Fig.  11. — Cast  of  shrinkage  cracks  (Carbon- 
iferous, Nova  Scotia),  illustrating  pre- 
tended AksB. 


LAURENTIAN   AXD  EARLY  PALEOZOIC. 


35 


by  Fleming  and  Carruthcrs  *  to  bo  casts  of  cavities  filled 
with  fluid,  abound  in  the  shales  of  the  Carboniferous  and 
Devonian.  They  are,  no  doubt,  in  most  cases  the  results 
of  the  pressure  and  consolidation  of  the  clay  around  small 
solid  bodies,  whether  organic,  fragmentary,  or  concre- 
tionary. They  are,  in  short,  local  slickensidcs  precisely 
similar  to  those  found  so  plentifully  in  the  coul  under- 
clays,  and  which,  as  I  have  elsewhere  f  shown,  resulted 
from  the  internal  giving  way  and  slipping  of  the  mass  as 
the  roots  of  Stigmaria  decayed  within  it.  Most  collectors 
of  fossil  plants  in  the  older  formations  must,  I  presume, 
be  familiar  with  appearances  of  this  kind  in  connection 
with  small  stems,  petioles,  fragments  of  wood,  and  car- 
polites.  I  have  in  my  collection  petioles  of  ferns  and 
fruits  of  the  genus  Trigonocarpum  partially  slickensided 
in  this  way,  and  which  if  wholly  covered  by  this  kind  of 
marking  could  scarcely  have  been  recognised.  I  have 
figured  bodies  of  this  kind  in  my  report  on  the  Devonian 
and  Upper  Silurian  plants  of  Canada,  believing  them, 
owing  to  their  carbonaceous  covering,  to  be  probably 
slickensided  fruits,  though  of  uncertain  nature.  In  every 
case  I  think  these  bodies  must  have  had  a  solid  nucleus  of 
some  sort,  as  the  severe  pressure  implied  in  slickensiding 
is  quite  incompatible  with  a  mere  ''fluid-cavity,"  even 
supposing  this  to  have  existed. 

Prof.  Marsh  has  well  explained  another  pliase  of  the 
influence  of  hard  bodies  in  producing  partial  slickensides, 
in  his  paper  on  Stylolites,  read  before  the  American  As- 
sociation in  1867,  and  the  application  of  the  combined 
forces  of  concretionary  action  and  slickensiding  to  the 
production  of  the  cone-in-cone  concretions,  which  occur 
in  the  coal-formation  and  as  low  as  the  Primordial.  I 
have  figured  a  very  perfect  and  beautiful  form  of  this 

*  "Journal  of  the  Geological  Society,"  June,  1871. 
f  Ibid.,  vol.  X.,  p.  14. 


0    0  0  '■> 


36 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


- 


kind  from  the  coal-formation  of  Nova  Scotia,  which  is 
described  in  **  Acadian  Geology"  *  (Fig.  12). 

I  have  referred  to  these  facts  here  because  they  are 
relatively  more  important  in  that  older  period,  which  may 
be  named  the  agt-  of  Algae,  and  because  their  settlement 
now  will  enable  us  to  dispense  with  discussions  of  this 
kind  further  on.  The  able  memoirs  of  Nathorst  and 
Williamson  should  be  studied  by  those  who  desire  further 
information. 

But  it  may  ba  as^^ed,  "Are  there  no  real  examples  of 
fossil  Algaj  ?  "  I  believe  there  are  many  such,  but  the  diffi- 
culty is  to  distinguish 
them.  Confining  our- 
selves to  the  older 
rocks,  the  following 
may  be  noted  : 

The  genus  Bu- 
thotrephis  of  Hall, 
which  is  characterised 
as  having  stems,  sub- 
cylindric  or  com- 
pressed, \vith  numer- 
ous branches,  which 
are  divaricating  and 
sometimes  leaf -like, 
contains  some  true  Algae.  Hall's  B.  gracilis,  from  the 
Siluro-Cambrian,  is  one  of  these.  Similar  plants,  referred 
to  the  same  species,  occur  in  the  Clinton  and  Niagara 
formations,  and  a  beautiful  species,  collected  by  Col. 
Grant,  of  Hamilton,  and  now  in  the  McGill  College  col- 
lection, represents  a  broader  and  more  frondose  type  of 
distinctly  carbonaceous  character.  It  may  be  described 
as  follows  : 

Buthotrephis  Grant ii,  S.  N    (Fig.  13). — Stems  and 

*  Appendix,  p.  676,  edition  of  1878. 


Fio.  12. — Cono-in-conc  concretion  (Carbon- 
iferouB,  Nova  Sootia),  illustrating  pre- 
tended Algee. 


,.,.^.n.^.uu.,r^m 


LAURENTIAN   AND  EARLY   PALEOZOIC. 


37 


fronds  smooth  and  slightly  striate  longitudinally,  with 
curved  and  intermixed  stria).  kStem  thick,  bifurcating, 
the  divisions  terminating  in  irregularly  pinnate  fronds, 
apparently  truncate  at  the  extremities.  The  quan- 
tity of  carbona- 
ceons  matter  pres- 
ent would  indicate 
thick,  though  per- 
haps flattened, 
stems  and  dense 
fleshy  fronds. 

The  species 
Butliotrcphis  sub- 
nodosa  and  B. 
jlexuosa,  from 
the  Utica  shale, 
are  also  certain- 
ly plants,  though 
it  is  possible,  if 
their  structures 
and  fruit  were 
known,  some  of 
these  might  be 
referred  to  differ- 
ent genera.  All 
of  these  plants 
have  either  car- 
bonacGous  matter 
or  produce  organ- 
ic stains  on  the 
matrix. 

The  organism 


Fio.  13. — Buffi  of  rep /lift  Grnnfii,  u  j»enuinc  Alga 
frum  the  Siluriun,  Ciinuda. 


diverging 


with 

wedge-shaped  fronds,  described  by  Hall  as  Sphenothalhis 
aiKjustifolius,  is  alsc  -i.  plant.  Fine  specimens,  in  the 
collection  of  the  Geologic^,!  Survey  of  Canada,  show  dis- 


38 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


tinct  evidence  of  the  organic  character  of  the  wedge- 
shaped  fronds.  It  is  from  the  Utica  shale,  and  elsewhere 
in  the  Siluro-Cambrian.  It  is  just  possible,  as  suggested 
by  Hall,  that  this  plant  may  be  of  higher  rank  than  the 
Algae. 

The  genus  Pdlmophycus  of  Hall  includes  a  great  va- 
n'ety  of  uncertain  objects,  of  which  only  a  few  are  prob- 
ably true  Algae.  I  have  specimens  of  fragments  sJT.ilar 
to  his  P.  virgatus,  which  show  distinct  carbonace«.'u8 
films,  and  others  from  the  Quebec  group,  which  seem  to 
be  cylindrical  tubes  now  flattened,  and  which  have  con- 
tained spindle-shaped  sporangia  of  large  size.  Tortuous 
and  curved  flattened  stems,  or  fronds,  from  the  Upper 
Silurian  limestone  of  Gaspe,  also  show  organic  matter. 

Respecting  the  forms  referred  to  Licrophycus  by 
Billings,  containing  stems  or  semi-cylindrical  markings 
springing  from  a  common  base,  I  have  been  in  great 
doubt.  I  have  not  seen  any  specimens  containing  une- 
quivocal organic  matter,  and  am  inclined  to  think  that 
most  of  them,  if  not  the  whole,  are  casts  of  worm-bur- 
rows, with  trails  radiating  from  them. 
f  Though  I  have  confined  myself  in  this  notice  to  plants, 
or  supposed  plants,  of  the  Lower  Palaeozoic,  it  may  be 
well  to  mention  the  remarkable  Cauda-Galli  fucoids,  re- 
ferred by  Hall  to  the  genus  Spirophyton,  and  which  are 
characteristic  of  the  oldest  Erian  beds.  The  specimens 
which  I  have  seen  from  New  York,  from  Gasp6,  and 
from  Brazil,  leave  no  doubt  in  my  mind  that  these  were 
really  marine  plants,  and  that  the  form  of  a  spiral  frond, 
assigned  to  them  by  Hall,  is  perfectly  correct.  They 
must  have  been  very  abundant  and  very  graceful  plants 
of  the  early  Erian,  immediately  after  the  close  of  the 
Silurian  period. 

We  come  now  to  notice  certain  organisms  referred  to 
Algae,  and  which  are  either  of  animal  origin,  or  are  of 
higher  grade  than  the  sea-weeds.     We  have  already  dis- 


LAURENTIAN  AND  EARLY  PALEOZOIC. 


39 


cussed  the  questions  relating  to  Prototaxites.  Drepano- 
phycus,  of  Goeppert,*  I  suspect,  is  only  a  badly  preserved 
branch  or  stem  of  the  Erian  land-plant  known  as  Arthro- 
stigma.  In  like  manner,  Haliserites  Dechenianus,\  of 
Goeppert,  is  evidently  the  land-plant  known  as  Psilophy- 
ton.  Sphcerococcites  dentatus  and  *S^.  serra — the  Fucoides 
dentatus  and  serra  of  Brongniart,  from  Quebec — are 
graptolites  of  two  species  quite  common  there.  J  Dic- 
tyopliyton  and  Uphantenia,  as  described  by  Hall  and  the 
author,  are  now  known  to  be  sponges.  They  have  be- 
come DictyospongicB.  The  curious  and  very  ancient  fos- 
sils referred  by  Forbes  to  the  genus  Oldhamia  are  perhaps 
still  subject  to  doubt,  but  are  usually  regarded  as  Zo- 
ophytes, though  it  is  quite  possible  they  may  be  plants. 
Though  I  have  not  seen  the  specimens,  I  have  no  doubt 
whatever  that  the  plants,  or  the  greater  part  of  them, 
from  the  Silurian  of  Bohemia,  described  by  Stur  as  Algae 
and  Characeae,*  are  really  land-plants,  some  of  them  of 
the  genus  Psilophyton.  I  may  say  in  this  connection 
that  specimens  of  flattened  Psilophyton  and  Arthrostig- 
ma,  in  the  Upper  Silurian  and  Erian  of  Gaspe,  would 
probably  have  been  referred  to  Algge,  but  for  the  fact  that 
in  some  of  them  the  axis  of  barred  vessels  is  preserved. 

It  is  not  surprising  that  great  difficulties  have  occurred 
in  the  determination  of  fossil  Algae.  Enough,  however, 
remains  certain  to  prove  that  the  old  Cambrian  and  Silu- 
r.an  seas  were  tenanted  with  sea-weeds  not  very  dissimilar 
from  those  of  the  present  time.  Ic  is  further  probable 
that  some  of  the  graphitic,  carbonaceous,  a-nd  bituminous 


*  "Fossile  Flora,"  1852,  p.  92,  Table  xli. 
f  Ibid.,  p.  88,  Table  ii. 

X  Brongniart,  "  Vegeteaux  Fossiles,"  Plate  vi.,  Figs.  7  to  12. 

*  "  Proceedings  of  the  Vienna  Academy,"  1881.  Hostinella,  of  this 
author,  is  almost  certainly  Psilophyton,  and  his  Barrandiana  seems  to  in- 
clude Arlhrostigma,  and  perhaps  leafy  branches  of  Berwynia.  These 
curious  plants  should  be  re-examined. 


40 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


i 


;i  U 


4 


shales  and  limestones  of  the  Silurian  owe  their  carbona- 
ceous matters  to  the  decomposition  of  Algse,  though  pos- 
sibly some  of  it  may  have  been  derived  from  Graptolites 
and  other  corneous  Zoophytes.     In  any  case,  such  micro- 


.;)6 


Fio.  14. — Silurian  vegetation  restored.    Protaiviularia^  Bertri/nia,  Kema- 
tophyton^  iiphenophyllum^  Arthrostiyma,  Bnlophyton. 


scopic  examinations  of  these  shales  as  I  have  made,  have 
not  produced  any  evidence  of  the  existence  of  plants  of 
higher  grade,  while  those  of  the  Erian  and  Carboniferous 
periocs,  similar  to  the  naked  eye,  abound  in  such  evi- 
dence.    It  is  also  to  be  observed  that,  on  the  surfaces  of 


■( 


r/^/»/«IA/VI/V/,^« 


LAURENTIAN  AND  EA.^LY  PALAEOZOIC. 


41 


beds  of  sandstone  in  the  Upper  Cambrian,  carbonaceous 
debris,  which  seems  to  be  the  remains  of  either  aquatic 
or  land  plants,  is  locally  not  infrequent. 

Referring  to  the  land  vegetation  of  the  older  rocks,  it 
is  difficult  to  picture  its  nature  and  appearance.  We 
may  imagine  the  shallow  waters  filled  with  aquatic  or  am- 
phibious Rhizocarpean  plants,  vast  meadows  or  brakes  of 
the  delicate  Psilophyton  and  the  starry  Protannularia 
and  some  tall  trees,  perhaps  looking  like  gigantic  club- 
mosses,  or  possibly  with  broad,  flabby  leaves,  mostly  cellu- 
lar in  texture,  and  resembling  Algae  transferred  to  the  air. 
Imagination  can,  however,  scarcely  realise  this  strange 
and  grotesque  vegetation,  which,  though  possibly  copious  . 
and  luxuriant,  must  have  been  simple  and  monotonous  iji^ 
aspect,  and,  though  it  must  have  produced  spores  and 
seeds  and  even  fruits,  these  were  probably  all  of  the  types 
seen  in  the  modern  acrogens  and  gymnosperms. 

"  In  garments  green,  indistinct  in  the  twilight, 
They  stand  like  Druids  of  old,  with  voices  sad  and  prophetic." 

Prophetic  they  truly  were,  as  we  shall  find,  of  the 
more  varied  forests  of  succeeding  times,  and  they  may 
also  help  us  to  realise  the  aspect  of  that  still  older  vege- 
tation, which  is  fossilised  in  the  Laurentian  graphite ; 
though  it  is  not  impossible  that  this  last  may  have  been  of 
higher  and  more  varied  types,  and  that  the  Cambrian  and 
Silurian  may  have  been  times  of  depression  in  the  vegeta- 
ble world,  as  they  certainly  were  in  the  submergence  of 
much  of  the  land. 

These  primeval  woods  served  at  least  to  clothe  the 
nakedness  of  the  new-born  land,  and  they  may  have  shel- 
tered and  nourished  forms  of  land-life  still  unknown  to 
us,  as  we  find  as  yet  only  a  few  insects  and  scorpions  in 
the  Silurian.  Tiiey  possibly  also  served  to  abstract  from 
the  atmosphere  some  portion  of  its  superabundant  car- 
bonic acid  harmful  to  animal  life,  and  they  stored  up 


42 


TJIE  GEOLOGICAL  HISTORY  OF  PLANTS. 


supplies  of  graphite,  of  petroleum,  and  of  illuminating 
gas,  useful  to  man  at  the  present  day.  We  may  write 
of  them  and  draw  their  forms  with  the  carbon  which 
they  themselves  supplied. 


i 


I  < 


t>4 


; 


I  i 


.      ^  NOTE  TO  CHAPTER  XL 

Examination  of  Prototaxites  {Nematopliyton),  by  Prof.  Pen- 
hallow,  OF  McGiLL  University. 

Prof.  Penhallow,  having  kindly  consented  to  re-examine  my 
specimens,  has  furnished  me  with  elaborate  notes  of  his  facts  and 
conclusions,  of  which  the  following  is  a  summary,  but  which  it  is 
hoped  will  be  published  in  full : 

"  1.  Concentric  Layers. — The  inner  face  of  each  of  these  is  com- 
posed of  relatively  large  tubes,  having  diameters  from  13'6  to  34"6 
micro-millimetres.  The  outer  face  has  tubes  ranging  from  13'8  to 
27"6  mm.  The  average  diameter  in  the  lower  surface  approaches  to  34, 
that  in  the  outer  to  13-8.  There  is,  however,  no  abrupt  termination 
to  the  surface  of  the  layers,  though  in  some  specimens  they  separate 
easily,  with  shining  surfaces. 

"3.  Minute  Structure. — In  longitudinal  sections  the  principal 
part  of  the  structure  consists  of  longitudinal  tubes  of  indeterminate 
length,  and  round  in  cross-section.  They  are  approximately  parallel, 
but  in  some  cases  may  be  seen  to  bend  sinuously,  and  are  not  in 
direct  contact.  Finer  myceloid  tubes,  5'33  mm.  in  diameter,  trav- 
erse the  structure  in  all  directions,  and  are  believed  to  branch  off 
from  the  larger  tubes.  In  a  small  specimen  supposed  to  be  a  branch 
or  small  stem,  and  in  which  the  vertical  tubes  are  somewhat  distant 
from  one  another,  this  horizontal  system  is  very  largely  developed; 
but  is  less  manifest  in  the  older  stems.  The  tubes  themselves  show 
no  structure.  The  ray-like  openings  in  the  substance  of  the  tissue 
are  evidently  original  parts  of  the  structure,  but  not  of  the  nature  of 
medullary  rays.  They  are  radiating  spaces  running  outward  in  an 
interrupted  manner  or  so  tortuously  that  they  appear  to  be  inter- 
rupted in  their  course  from  the  centre  towards  the  surface.  They 
show  tubes  turnmg  into  them,  branching  into  them,  and  approxi- 
mately horizontal,  but  tortuous.  On  the  external  surface  of  some 
specimens  these  radial  spaces  are  represented  by  minute  pits  irregu- 


^...r.n,.^.uunr^m 


LALTvENTIAN    AND  EARLY   PALEOZOIC. 


48 


larly  or  spirally  arranged.  The  transverse  swellings  of  the  stem 
show  no  difference  of  structure,  except  that  the  tubes  or  cells  may  be 
a  little  more  tortuous,  and  a  transverse  film  of  coaly  matter  extends 
from  the  outer  coaly  envelope  inwardly.  This  may  perhaps  be 
caused  by  some  accident  of  preservation.  The  outer  coaly  layer 
shows  tubes  similar  to  those  of  the  stem.*  The  horizontal  or  oblique 
flexures  of  the  large  tubes  seem  to  be  mainly  in  the  vicinity  of  the 
radial  openings,  and  it  is  in  entering  these  that  they  have  been  seen 
to  branch." 

The  conclusions  arrived  at  by  Prof.  Penhallow  are  as  follows  : 

"  1.  The  plant  was  not  truly  exogenous,  and  the  appearance  of 
rings  is  independent  of  the  causes  which  determine  the  layers  of 
growth  in  exogenous  plants. 

"  2.  The  plant  was  possessed  of  no  true  bark.  Whatever  cortical 
layer  was  present  was  in  all  probability  a  modification  of  the  general 
structure,  f 

"3.  An  intimate  relation  exists  between  the  large  tubular  cells 
and  the  myceloid  filaments,  the  latter  being  a  system  of  small 
branches  from  the  former ;  the  branching  being  determined  chiefly  in 
certain  special  openings  which  simulate  medullary  rays. 

"  4.  The  specimens  examined  exhibit  no  evidence  of  special  de- 
cay, and  the  structure  throughout  is  of  a  normal  character. 

"  5.  The  primary  structure  consists  of  large  tubular  ce)ls  without 
apparent  terminations,  and  devoid  of  structural  markings,  with 
which  is  associated  a  secondary  structure  of  myceloid  filaments  aris- 
ing from  the  former. 

"  6.  The  structure  of  Nematophyton  as  a  whole  is  unique ;  at  least 
there  is  no  plant  of  modern  type  with  which  it  is  comparable. 
Nevertheless,  the  loose  character  of  the  entire  structure ;  the  inter- 
minable cells;  their  interlacing;  and,  finally,  their  branching  into  a 
secondary  series  of  smaller  filaments,  point  with  considerable  force  to 
the  true  relationship  of  the  stem  as  being  with  Algae  or  other  Thallo- 
phytes  rather  than  with  Gymnosperms.    A  more  recent  examination 

*  It  is  possible  that  these  tubes  may  be  merely  part  of  the  stem  at- 
tached to  the  bark,  which  seems  to  me  to  indicate  the  same  dense  cellular 
structure  seen  in  the  bark  of  Lepidodc7idra,  etc. 

f  On  these  points  I  would  reserve  the  considerations ;  1.  That  there 
must  have  been  some  relation  between  the  mode  of  growth  of  these  great 
stems  and  their  concentric  rings  ;  and,  2.  That  the  evidence  of  a  bark  is 
as  strong  as  in  the  case  of  any  Palaeozoic  tree  in  which  the  bark  is,  aa 
usual,  carbonised. 


• 


wf 


44 


THE   GEOLOGICAL   HISTORY  OF  PLANTS. 


of  a  laminated  resinous  substance  found  associated  with  the  plant 
shows  that  it  is  wholly  amorphous,  and,  as  indicated  by  distinct  lines 
of  flow,  that  it  must  have  been  in  a  plastic  state  at  a  former  period. 
The  only  evidence  of  structure  was  found  in  certain  well-deflned 
mycelia,  which  may  have  been  derived  from  associated  vegetable 
matter  upon  which  they  were  growing,  and  over  which  the  plastic 
matrix  flowed." 

1  have  only  to  add  to  this  description  that  when  we  consider  that 
Nematophyton  Logani  was  a  large  tree,  sometimes  attaining  a  diam- 
eter of  more  than  two  feet,  and  a  stature  of  at  least  twenty  before 
branching ;  that  it  had  great  roots,  and  gave  off  large  branches ;  that 
it  was  an  aerial  plant,  probably  flourishing  in  the  same  swampy  flats 
with  Psilophyton,  Arthrostigtna,  and  Leptophleum  ;  that  the  peculiar 
bodies  known  as  Pachytheca  were  not  unlikely  its  fruit — we  have 
evidence  that  there  were,  in  the  early  Palaeozoic  period,  plants 
scarcely  dreamt  of  by  modern  botany.  Only  when  the  appendages 
of  these  plants  are  more  fully  known  can  we  hope  to  understand 
them.  In  the  mean  time,  I  may  state  that  there  were  probably  differ- 
ent species  of  these  trees,  indicated  more  particularly  by  the  stems  I 
have  described  as  Nematoxylon  and  Celluloxylon.*  There  were,  I 
think,  some  indications  that  the  plants  described  by  Carruthers  as 
Berwynia,  may  also  be  found  to  have  been  generically  the  same. 
The  resinous  matter  mentioned  by  Prof.  Penhallow  is  found  in  great 
abundance  in  the  beds  containing  Nem.  *ophyton,  and  must,  I  think, 
have  been  an  exudation  from  its  bark. 

*  "Journal  Geol.  Society  of  London,"  1863,  1881. 


CHAPTER  III. 


THE   ERIAN   OR    DEVONIAN    FORESTS — ORIGIN   OF   PETRO- 
LEUM— THE  AGE   OF   ACROGENS  AND  GYMNOSPERMS. 

In  the  last  chapter  we  were  occupied  with  the  com- 
paratively few  and  obscure  remains  of  plants  entombed 
in  the  oldest  geological  formations.  We  now  ascend  to  a 
higher  plane,  that  of  the  Erian  or  Devonian  period,  in 
which,  for  the  first  time,  we  find  varied  and  widely  dis- 
tributed, forests. 

The  growth  of  knowledge  with  respect  to  this  flora 
has  been  somewhat  rapid,  and  it  may  be  interesting  to 
note  its  principal  stages,  as  an  encouragement  to  the  hope 
that  we  may  yet  learn  something  more  satisfactory  re- 
specting the  older  floras  we  have  just  discussed. 

In  Goeppert's  memoir  on  the  flora  of  the  Silurian, 
Devonian,  and  Lower  Carboniferous  rocks,  published  in 
I860,*  he  enumerates  twenty  species  as  Silurian,  but  these 
are  all  admitted  to  be  Algae,  and  several  of  them  are  re- 
mains which  mnv  be  fairly  claimed  by  the  zoologists  as 
zoophytes,  or  tr  s  of  worms  and  mollusks.  In  the  Lower 
Devonian  he  knows  but  six  species,  five  of  which  are 
Algae,  and.  the  remaining  one  a  Sif/illaria,  but  this  is  of 
very  doubtful  nature.  In  the  Middle  Devonian  he  gives 
but  one  species,  a  land-plant  of  the  genus  Lepidodcndron. 
In  the  Upper  Devonian  the  number  rises  to  fifty-seven, 
of  which  all  but  seven  are  terrestrial  plants,  representing 

*  Jena,  1860. 


' 


1 . 

.1 

Pt-      -   j 

W    ' 

p   1 

W- 

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46 


THE  GEOLOGICAL   UISTORY  OF  PLANTS. 


a  large  number  of  the  genera  occurring  in  the  succeeding 
Carboniferous  system. 

Goeppert  does  not  inchide  in  his  enumeration  the 
plants  from  the  Devonian  of  Gaspe,  described  by  the 
author  in  1859,*  having  seen  only  an  abstract  of  the 
paper  at  the  time  of  writing  his  memoir,  nor  does  he 
appear  to  have  any  knowledge  of  the  plants  of  this  age 
described  by  Lcsquereux  in  Rogers's  **  Pennsylvania." 
These  might  have  added  ten  or  twelve  species  to  his  list, 
some  of  them  probably  from  the  Lower  Devonian.  It  is 
further  to  be  observed  that  a  few  additional  species  had 
also  been  recognised  by  Peach  in  the  Old  Red  Sandstone 
of  Scotland. 

But  fiom  1860  to  the  present  time  a  rich  harvest  of 
specimens  has  been  gathered  from  the  Gaspe  sandstones, 
from  the  shales  of  southern  New  Brunswick,  from  the 
sandstones  of  Perry  in  Maine,  and  from  the  wide-spread 
Erian  areas  of  New  York,  Pennsylvania,  and  Ohio. 
Nearly  all  tiiese  specimens  have  passed  through  my 
hands,  and  I  am  now  able  to  catalogue  about  a  hun- 
dred species,  representing  more  than  thirty  genera,  and 
including  all  the  great  types  of  vascular  Cryptogams,  the 
Gymnosperms,  and  even  one  (still  doubtful)  Angiosperm. 
Many  new  forms  have  also  been  described  from  the  De- 
vonian of  Scotland  and  of  the  Continent  of  Europe. 

Before  describing  these  plants  in  detail,  we  may  refer 
to  North  America  for  illustration  of  the  physical  condi- 
tions of  the  time.  In  a  physical  point  of  view  the  north- 
ern hemisphere  presented  a  great  change  in  the  Erian 
period.  There  were  vast  foldings  of  the  crust  of  the 
earth,  and  great  emissions  of  volcanic  rock  on  both  sides 
of  the  Atlantic.  In  North  America,  while  at  one  time 
the  whole  interior  area  of  the  continent,  as  far  north  as 

*  "  Journal  of  the  Geological  Society  of  London,"  also  "  Canadian 
Naturalist." 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


47 


the  Great  Lakes,  was  occupied  by  a  vast  inland  sea,  studded 
with  coral  islands,  the  long  Appalachian  ridge  had  begun 
to  assume,  along  with  the  old  Laurentian  land,  something 
of  the  form  of  our  present  continent,  and  on  the  margins 
of  this  Appalachian  belt  there  were  wide,  swampy  flats  and 
shallow-Avater  areas,  which,  under  the  mild  climate  that 
seems  to  have  characterised  this  period,  were  admirably 
suited  to  nounsh  a  luxuriant  vegetation.  Under  this 
mild  climate,  also,  it  would  seem  that  new  forms  of  plants 
were  first  introduced  in  the  far  north,  where  the  long 
continuance  of  summer  sunlight,  along  with  great  warmth, 
seems  to  have  aided  in  their  introduction  and  early  ex- 
tension, and  thence  made  their  way  to  the  southward,  a 
process  which,  as  Gray  and  others  have  shown,  has  also 
occurred  in  later  geological  times. 

The  America  of  this  Erian  age  consisted  during  the 
greater  part  of  the  period  of  a  more  or  less  extensive  belt 
of  land  in  the  north  with  two  long  tongues  descending 
from  it,  one  along  the  Appalachian  line  in  the  east,  the 
other  in  the  region  west  of  the  Rocky  Mountains.  On 
the  seaward  sides  of  these  there  were  low  lands  covered 
witli  vegetation,  while  on  the  inland  side  the  great  in- 
terior sea,  with  its  verdant  and  wooded  islands,  realised, 
though  probably  with  shallower  water,  the  conditions  of 
the  modern  archipelagoes  of  the  Pacific. 

Europe  presented  conditions  somewhat  similar,  having 
in  the  earlier  and  middle  portions  of  the  period  great  sea 
areas  with  insular  patches  of  land,  and  later  wide  tracts 
of  shallow  and  in  part  enclosed  water  areas,  swarming 
with  fishes,  and  having  an  abundant  vegetation  on  their 
shores.  These  were  the  conditions  of  the  Eifel  and 
Devonshire  limestones,  and  of  the  Old  Red  Sandstone  of 
Scotland,  and  the  Kiltorcan  beds  of  Ireland.  In  Europe 
also,  as  in  America,  there  were  in  the  Eriim  age  great 
ejections  of  igneous  rock.  On  both  sides  of  the  Atlantic 
there  were  somewhat  varied  and  changing  conditions  of 


I  ii 


48 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


(I 


land  and  water,  and  a  mild  and  equable  climate,  permit- 
ting the  existence  of  a  rich  vegetation  in  high  northern 
latitudes.  Of  this  latter  fact  a  remarkable  example  is 
afforded  by  the  beds  holding  plants  of  this  age  in  Spitz- 
bergen  and  Bear  Island,  in  its  vicinity.  Here  there  seem 
to  be  two  series  of  plant-bearing  strata,  one  with  the 
vegetation  of  the  Upper  Erian,  the  other  with  that  of 
the  Lower  Carboniferous,  though  both  have  been  united 
by  Heer  under  his  so-called  "Ursa  Stage,"  in  which  he 
has  grouped  the  characteristic  plants  of  two  distinct 
periods.  This  has  recently  been  fully  established  by  the 
researches  of  Nathorst,  though  the  author  had  already 
suggested  it  as  the  probable  explanation  of  the  strange 
union  of  species  in  the  Ursa  group  of  Heer. 

In  studying  the  vegetation  of  this  remarkable  period, 
we  must  take  merely  some  of  the  more  important  forms 
as  examples,  since  it  would  be  impossible  to  notice  all 
the  species,  and  some  of  them  may  be  better  treated  in 
the  Carboniferous,  where  they  have  their  headquarters. 
(Fig.  15.) 

I  may  first  refer  to  a  family  which  seems  to  have  cul- 
minated in  the  Erian  age,  and  ever  since  to  have  occupied 
a  less  important  place.  It  is  that  of  the  curious  aquatic 
plants  known  as  Rhizocarps,*  and  referred  to  in  the  last 
chapter. 

My  attention  was  first  directed  to  these  organisms  by 
the  late  Sir  W.  E.  Logan  in  18G9.  He  had  obtained  from 
the  Upper  Erian  shale  of  Kettle  Point,  Lake  Huron, 
specimens  filled  with  minute  circular  discs,  to  which  he 
referred,  in  his  report  of  1863,  as  "microscopic  orbicular 
bodies."  Recognising  them  to  be  macrospores,  or  spore- 
cases,  I  introduced  them  into  the  report  on  the  Erian 

*  Or,  as  they  have  recently  been  named  by  some  botanists,  "Ilete- 
rosporous  Filices,"  though  they  are  certainly  not  ferns  in  any  ordinary 
sense  of  that  term. 


I 


ill 


1 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


49 


flora,  which  I  was  then  preparing,  and  which  was  pub- 
lished in  1871,  under  the  name  Sporangites  Huronensis. 
In  1871,  having  occasion  to  write  a  communication  to 
the  "American  Journal  of  Science"  on  the  question  then 


FiQ.  15. — Vegetation  of  the  Devonian  period,  restored.  Catamites,  I^lo- 
phi/ton,  Zepiophleum,  Zeptdodendron,  Vordaites,  SitjiUaria,  Dadoxy- 
loUy  Aster oph'jllites,  PlatypJiijUum. 

raised  as  to  the  sliare  of  spores  and  spore-cases  in  the  ac- 
cumulation of  coal,  a  question  to  be  discussed  in  a  sub- 


f! 


I 


i  \ 


*:t  i 


I 


60 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


sequent  chapter,  these  curious  little  bodies  were  again 
reviewed,  and  were  described  in  substance  as  follows  : 

'*  The  oldest  bed  of  spore-cases  known  to  me  is  that 
at  Kettle  Point,  Lake  Huron.  It  is  a  bed  of  brown 
bituminous  shale,  burning  with  much  flame,  and  under 
a  lens  is  seen  to  be  studded  with  flattened  disc-like  bodies, 
scarcely  more  than  a  hundredth  of  an  inch  in  diameter, 
which  under  the  microscope  are  found  to  be  spore-cases 
(or  macrospores)  slightly  papillate  externally  (or  more 
properly  marked  with  dark  pores),  and  sometimes  show- 
ing a  point  of  attachment  on  one  side  and  a  slit  more  or 
less  elongated  and  gaping  on  the  other.  When  slices  of 
the  rock  are  made,  its  substance  is  seen  to  be  filled  with 
these  bodies,  which,  viewed  as  transparent  objects,  appear 
yellow  like  amber,  and  show  little  structure,  except  that 
the  walls  can  be  distinguished  from  the  internal  cavity, 
which  may  sometimes  be  seen  to  enclose  patches  of  granu- 
lar matter.  In  the  shale  containing  them  are  also  vast 
numbers  of  rounded,  translucent  granules,  which  may  be 
escaped  spores  (microspores)."  The  bed  containing  these 
spores  at  Kettle  Point  was  stated,  in  the  reports  of  the 
"Geological  Survey  of  Canada,"  to  be  twelve  or  fourteen 
feet  in  thickness,  and  besides  these  specimens  it  contained 
fossil  plants  referable  to  the  species  Calamites  inornatus 
and  Lepidodendro7i  primcevum,  and  I  not  unnaturally 
supposed  that  the  Sporangites  might  be  the  fruit  of  tlie 
latter  plant.  I  also  noticed  their  resemblance  to  the 
spore-cases  of  L.  corrugotum  of  the  Lower  Carboniferous 
(a  Lepidodendron  allied  to  L.  primwvum),  and  to  those 
from  Brazil  described  by  Carruthers  under  the  name 
Flemingitcs,  as  well  as  to  those  described  by  Huxley 
from  certain  English  coals,  and  to  those  of  the  Tasmanite 
or  white  coal  of  Australia.  The  bed  at  Kettle  Point  is 
shown  to  be  marine  by  its  holding  the  sea-weed  known 
as  Spirophi/ion,  and  shells  of  Linyula. 

The  subject  did  not  again  come  under  my  notice  till 


THE  BRIAN  OR   DEVONIAN  FORESTS. 


61 


1883,  when  Prof.  Orton,  of  Columbus,  Ohio,  sent  me 
some  specimens  from  the  Erian  shales  of  that  State, 
wiiich  on  comparison  seemed  undistinguishable  from 
Sporangites  Huronensis.*  Prof.  Orton  read  an  interest- 
ing paper  on  these  bodies,  at  the  meeting  of  the  American 
Association  in  Montreal,  in  which  were  some  new  and 
striking  facts.  One  of  these  was  the  occurrence  of  such 
bodies  throughout  the  black  shales  of  Ohio,  extending 
**from  the  Huron  River,  on  the  shore  of  Lake  Erie,  to 
the  mouth  of  the  Scioto,  in  the  Ohio  Valley,  with  an 
extent  varying  from  ten  to  twenty  miles  in  breadth,"  and 
estimated  to  be  three  hundred  and  fifty  feet  in  thickness. 
I  have  since  been  informed  by  my  friend  Mr.  Thomas,  of 
Chicago,  that  its  thickness,  in  some  places  at  least,  must 
be  three  times  that  amount.  About  the  same  time,  Prof. 
Williams,  of  Cornell,  and  Prof.  Clarke,  of  Northampton, 
announced  similar  discoveries  in  the  State  of  New  York, 
so  that  it  would  appear  that  beds  of  vast  area  and  of  great 
thickness  are  replete  with  these  little  vegetable  discs,  usu- 
ally converted  into  a  highly  bituminous,  amber-like  sub- 
stance, giving  a  more  or  less  inflammable  character  to  the 
containing  rock. 

Another  fact  insisted  on  by  Prof.  Orton  was  the  ab- 
sence of  Le])idodendroid  cones,  and  the  occurrence  of 
filamentous  vegetable  matter,  to  which  the  Sporangites 
seemed  to  be  in  some  cases  attached  in  groups.  Prof. 
Orton  also  noticed  the  absence  of  the  trigonal  form,  which 
belongs  to  the  spores  of  many  Lepidodendra,  though  this 
is  not  a  constant  character.  In  the  discussion  on  Prof. 
Orton's  paper,  I  admitted  that  the  facts  detailed  by  him 
shook  my  previous  belief  of  the  lycopodiaceous  character 


*  These  shales  have  been  described,  as  to  their  chemical  and  geological 
relations,  by  Dr.  T.  Sterry  Hunt,  "American  Journal  of  Science,"  1803, 
and  by  Dr.  Newberry,  in  the  "  Reports  of  the  Geological  Survey  of  Ohio," 
vol.  i.,  1863,  and  vol.  iii.,  1878. 


"TT 


62 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


' 


P 


I 


t 


ti: 


ft  t 


of  these  bodies,  and  induced  me  to  suspect,  with  Prof. 
Orton,  that  they  might  have  belonged  to  some  group  of 
aquatic  plants  lower  than  the  Lycopods. 

Since  the  publication  of  my  paper  on  Rhizocarps  in 
the  PalaBOzoic  period  above  referred  to,  I  have  received 
two  papers  from  Mr.  Edward  Wethered,  F.  G.  S.,  in  one 
of  which  he  describes  spores  of  plants  found  in  the  lower 
limestone  shales  of  the  Forest  of  Dean,  and  in  the  other 
discusses  more  generally  the  structure  and  origin  of  Car- 
boniferous coal-beds.*  In  both  papers  he  refers  to  the 
occurrence  in  these  coals  and  shales  of  organisms  essen- 
tially similar  to  the  Brian  spores. 

In  the  "Bulletin  of  the  Chicago  Academy  of  Science," 
January,  1884,  Dr.  Johnson  and  Mr.  Thomas,  in  their 
paper  on  the  **  Microscopic  Organisms  of  the  Boulder  Clay 
of  Chicago  and  Vicinity,"  notice  Sporangites  Huronensis 
as  among  these  organisms,  and  have  discovered  them  also 
in  large  numbers  in  the  precipitate  from  Chicago  city 
water-supply.  They  refer  them  to  the  decomposition  of 
the  Brian  shaies,  of  which  boulders  filled  with  these  or- 
ganisms are  of  frequent  occurrence  in  the  Chicago  clays. 
The  Sporangites  and  their  accompaniments  in  the  boulder 
clay  are  noticed  in  a  paper  by  Dr.  G.  M.  Dawson,  in  the 
"Bulletin  of  the  Chicago  Academy,"  June,  1885. 

Prof.  Clarke  has  also  described,  in  the  "American 
Journal  of  Science"  for  April,  1885,  the  forms  already 
alluded  to,  and  v/hich  he  finds  to  consist  of  microspores 
enclosed  in  sporocarps.  He  compares  these  with  my 
Spora7igites  Huronensis  and  Protosalvinia  bilohata,  but 
I  think  it  is  likely  that  one  of  them  at  least  is  a  distinct 
species. 

I  may  add  that  in  the  "Geological  Magazine"  for 
1875,  Mr.  Newton,  F.  G.  S.,  of  the  Geological  Survey  of 

*  " Cotteswold   Naturalists'  Field   Club,"    1884;    "Journal  of  the 
Royal  Microscopic  '  Society,"  1885. 


'■S 


THE  ERLVN  OR  DEVONIAN  FORESTS. 


53 


» 


England,  published  a  description  of  the  Tasmanite  and 
Australian  white  coal,  in  which  he  shows  that  the  or- 
ganisms in  these  deposits  are  similar  to  my  Sporangites 
Huronensis,  and  to  the  macrospores  previously  described 
by  Prof.  Huxley,  from  the  Better-bed  coal.  Mr.  Newton 
does  not  seem  to  have  been  aware  of  my  previous  descrip- 
tion of  Sporangites,  and  proposes  the  name  Tasmanites 
punctatus  for  the  Australian  form. 

Here  we  have  the  remarkable  fact  that  the  waste 
macrospores,  or  larger  spores  of  a  species  of  Cryptoga- 
mous  plant,  occur  dispersed  in  countless  millions  of  tons 
through  the  shales  of  the  Erian  in  Canaaa  and  the  United 
States. 

No  certain  clue  seemed  to  be  afforded  by  all  these 
observations  as  to  the  precise  affinities  of  these  widely 
distributed  bodies  ;  but  this  was  furnished  shortly  after 
from  an  unexpected  quarter.  In  March,  1883,  Mr.  Or- 
ville  Derby,  of  the  Geological  Survey  of  Brazil,  sent  me 
specimens  found  in  the  Erian  of  that  country,  which 
seemed  to  throw  a  new  light  on  the  whole  subject.  These 
I  described  and  pointed  out  their  connection  with  Sporan- 
gites at  the  meeting  of  the  American  Association  at  Min- 
neapolis, in  1883,  and  subsequently  published  my  notes 
respecting  them  in  its  proceedings,  and  in  the  ''Canadian 
Record  of  Science." 

Mr.  Derby's  specimens  contained  the  curious  «^piral 
sea-weed  known  as  Spiropliyton,  and  also  minute  rounded 
Sporangites  like  those  obtained  in  the  Erian  of  Ohio,  and 
of  which  specimens  had  been  sent  to  me  some  years  be- 
fore by  tlie  late  Prof.  Hartt.  But  they  differed  in  show- 
ing tlie  remarkable  fact  tliat  these  rounded  bodies  are 
enclosed  in  considerable  numbers  in  spherical  and  oval 
sacs,  the  walls  of  Avhicli  are  composed  of  a  tissue  of 
hexagonal  cells,  and  which  resemble  in  every  respect  the 
involucres  or  spore-sacs  of  the  little  group  of  modern 
acrogens  known  as  Rhizocarps,   and   living  in  shallow 


64 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


water.  More  especially  they  resemble  the  sporocarps  of 
the  genus  Salvinia.  This  fact  opened  up  an  entirely 
new  field  of  investigation,  and  I  at  once  proceeded  to 
compare  the  specimens  with  the  fructification  of  modern 
Rhizocarps,  and  found  that  substantially  these  multitu- 
dinous spores  embedded  in  the  Erie  shales  may  be  re- 
garded as  perfectly  analogous  to  the  larger  spores  of  the 
modern  Salvinia  natans  of  Europe,  as  may  be  seen  by 
the  representation  of  them  in  Fig.  16. 


® 


AX 


yix 


DX 


Fig.  16. — Sporangites  {I^otoaahinia).  a.  Sporangites  Brasiliends,  natural 
Bize.  AX,  Same,  magnified,  b,  Sp.  biloba,  natural  size,  c,  Detached 
umerosporos.  n,  Spore-cases  of  5fl«'»«trt  iiatans.  dx.  Same,  magnitied. 
E,  Shale  with  sporangites,  vertical  section,  highly  magnified. 


Ill 


The  typical  macrospores  from  the  Erian  shales  are 
perfectly  circular  in  outline,  and  in  the  flattened  state  ap- 
pear as  discs  with  rounded  edges,  their  ordinary  diameter 
being  from  one  seventy-fifth  to  one  one  hundredth  of  an 
inch,  though  they  vary  considerably  in  size.  This,  how- 
ever, I  do  not  regard  as  an  essential  character.  The 
edges,  as  seen  in  profile,  are  smooth,  but  the  flat  surface 
often  presents  minute  dark  spots,  which  at  first  I  mis- 


THE  ERIAN   OR  DEVONIAN  FORESTS, 


65 


took  for  papillse,  but  now  agree  with  Mr.  Thomas  in  rec- 
ognising them  as  minute  prres  traversing  the  wall  of  the 
disc,  and  similar  to  those  which  Mr.  Newton  has  described 
in  Tasmanite,  and  which  Mr.  Wethered  has  also  recog- 
nised in  the  similar  spores  of  the  Forest  of  Dean  shales. 
The  walls  also  sometimes  show  faint  indications  of  con- 
centric lamination,  as  if  they  had  been  thickened  by  suc- 
cessive deposits. 

As  seen  by  transmitted  light,  and  either  in  front  or  in 
profile,  the  discs  are  of  a  rich  amber  colour,  translucent 
and  structureless,  except  the  pores  above  referred  to. 
The  wails  are  somewhat  thick,  or  from  one-tenth  to  one- 
twentieth  the  diameter  of  the  disc  in  thickness.  They 
never  exhibit  the  triradiate  marking  seen  in  spores  of  Ly- 
copods,  nor  any  definite  point  of  attachment,  though 
they  sometimes  show  a  minute  elongated  spot  which  may 
be  of  this  nature,  and  they  are  occasionally  seen  to  have 
opened  by  slits  on  the  edge  or  front,  where  there  would 
seem  to  have  been  a  natural  line  of  dehiscence.  The  in- 
terior is  usually  quite  vacant  or  structureless,  but  in  some 
caries  there  are  curved  internal  markings  which  may  indi- 
cate a  shrunken  lining  memorane,  or  the  remains  of  a 
prothallus  or  embryo.  Occasionally  a  fine  granular  sub- 
stance appears  in  the  interior,  possibly  remains  of  mi- 
crospores. 

The  discs  are  usually  detached  and  destitute  of  any 
envelope,  but  fragments  of  flocculent  cellular  matter  are 
associated  with  them,  and  in  one  specimen  from  the  cor- 
niferous  limestone  of  Ohio,  in  Mr.  Thomas's  collection,  I 
have  found  a  group  of  eight  or  more  discs  partly  enclosed 
in  a  cellular  sac-like  membrane  of  similar  character  to 
that  enclosing  the  Brazilian  specimens  already  referred  to. 

The  characters  of  all  the  specimens  are  essentially 
similar,  and  there  is  a  remarkable  absence  of  other  organ- 
isms in  the  shale.  In  one  instance  only,  I  have  observed 
a  somewhat  smaller  round  body  with  a  dark  centre  or 


56 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


1       "     ' 


nucleus,  and  a  wide  translucent  margin,  marked  by  a 
slight  granulation.  Even  this,  however,  may  indicate 
nothing  more  than  a  different  state  of  preservation. 

It  is  proper  to  observe  here  that  the  wall  or  enclosing 
sac  of  these  macrospores  must  have  been  of  very  dense 
consistency,  and  now  appears  as  a  highly  bituminous  sub- 
stance, in  this  agreeing  with  that  of  the  spores  of  Lyco- 
pods,  and,  like  them,  having  been  when  recent  of  a  highly 
carbonaceous  and  hydrogenous  quality,  very  combustible 
and  readily  admitting  of  change  into  bituminous  matter. 
In  the  paper  already  referred  to,  on  spore-cases  in  coals, 
I  have  noticed  that  the  relative  composition  of  lyco- 
podium  and  cellulose  is  as  follows  : 

Cellulose,  CgiHgoOgo* 

Lycopodium,  C43H19.NO5-. 

Thus,  such  spores  are  admirably  suited  for  the  pro- 
duction of  highly  carbonaceous  or  bituminous  coals,  etc. 

Nothing  is  more  remarkable  in  connection  with  these 
bodies  than  their  uniformity  of  structure  and  form  over 
so  great  areas  and  throughout  so  great  thickness  of  rock, 
and  the  absence  of  any  other  kind  of  spore-case.  This 
is  more  especially  noteworthy  in  contrast  with  the  coarse 
coals  and  bituminous  shales  of  the  Carboniferous,  which 
usually  contain  a  great  variety  of  spores  and  sporangia, 
indicating  the  presence  of  many  species  of  acrogenous 
plants,  while  the  Erian  shales,  on  the  contrary,  indicate  the 
almost  exclusive  predominance  of  one  form.  This  con- 
trast is  well  seen  in  the  Bedford  shales  overlying  these 
beds,  and  I  believe  Lower  Carboniferous.*  Specimens  of 
these  have  been  kindly  communicated  to  me  by  Prof. 
Orton,  and  have  been  prepared  by  Mr.  Thomas.  In  these 
we  see  the  familiar  Carboniferous  spores  with  triradiate 
markings  called  Triletes  by  Reinsch,  and  which  are  simi- 
lar to  those  of  Lycopodiaceous  plants.     Still  more  abun- 

*  According  to  Newberry,  lower  part  of  Waverly  group. 


IL 


THE  BRIAN   OR  DEVONIAN  FORESTS. 


57 


id  by  a 
indicate 
m. 

nclosing 
ry  dense 
lous  sub- 
)f  Lyco- 
a  highly 
ibustible 
i  matter, 
in  coals, 
of  lyco- 


the  pro- 

•als,  etc. 

ith  these 

orni  over 

of  rock, 

ie.     This 

he  coarse 

is,  which 

Dorangia, 

rogenous 

licate  the 

^his  con- 

ng  these 

3imens  of 

by  Prof. 

In  these 

triradiate 

are  simi- 

ore  abun- 

up. 


dant  are  those  spinous  and  hooked  spores  or  sporangia, 
to  which  the  names  Sporocarpon,  Zygosporites,  and  Tra- 
quaria  have  been  given,  and  some  of  which  Williamson 
has  shown  to  be  spores  of  Lycopodiaceous  plants.* 

The  true  ''Sporangites,"  on  the  contrary,  are  round 
and  smooth,  with  thick  bituminous  walls,  which  are 
punctured  with  minute  transverse  pores.  In  these  re- 
spects, as  already  stated,  they  closely  resemble  the  bodies 
found  in  the  Australian  white  coal  and  Tasmanite.  The 
precise  geological  age  of  this  last  material  is  not  known 
with  certainty,  but  it  is  believed  to  be  Palaeozoic. 

With  reference  to  the  mode  of  occurrence  of  these 
bodies,  we  may  note  first  their  great  abundance  and  wide 
distribution.  The  horizontal  range  of  the  bed  at  Kettle 
Point  is  not  certainly  known,  but  it  is  merely  a  northern 
outlier  of  the  great  belt  of  Erian  shales  referred  to  by 
Prof.  Ortou,  and  which  extends,  with  a  breadth  of  ten  to 
twenty  miles,  and  of  great  thickness,  across  the  State  of 
Ohio,  for  nearly  two  hundred  miles.  This  Ohio  black 
shale,  which  lies  at  the  top  of  the  Erian  or  the  base  of 
the  Carboniferous,  though  probably  mainly  of  Erian  age, 
appears  to  abound  throughout  in  these  organisms,  and  in 
some  beds  to  be  replete  with  them.  In  like  manner,  in 
Brazil,  according  to  Mr.  Derby,  these  organisms  are  dis- 
tributed over  a  wide  area  and  throughout  a  great  thick- 
ness of  shale  holding  Spirophyton,  and  apparently  belong- 
ing to  the  Upper  Erian.  The  recurrence  of  similar  forms 
in  the  Tasmanite  and  white  coal  of  Tasmania  and  Aus- 
tralia is  another  important  fact  of  distribution.     To  this 

*  Traquaria  is  to  be  distinguished  from  the  calcareous  bodies  found 
in  the  corniferous  limestone  of  Kelly's  Island,  which  I  have  described  in 
the  "  Canadian  Naturalist  "  as  Saccamina  Eriana,  and  believe  to  be  Fo- 
raminiferal  tests.  They  have  since  been  described  by  Ulrich  under  a 
different  name  {Mallerina:  contribution  to  "American  Palaeontology," 
1886).  Sec  Dr.  Williamson's  papers  in  "Transactions  of  Royal  Society 
of  London." 


ff8 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


we  may  add  the  appearance  of  these  macrospores  in  coals 
and  shales  of  the  Carboniferous  period,  tliough  there  in 
association  with  other  forms. 

It  is  also  to  be  observed  that  the  Erian  shales,  and  the 
Forest  of  Dean  beds  described  by  Wethered,  are  marine, 
as  shown  by  their  contained  fossils ;  and,  though  I  have 
no  certain  information  as  to  the  Tasmanite  and  Austra- 
lian white  coal,  they  would  seem,  from  the  description  of 
Milligan,  to  occur  in  distinctly  aqueous,  possibly  estua- 
rine,  deposits.  Wethered  has  shown  that  the  discs  de- 
scribed by  Huxley  and  Newton  in  the  Better-bed  coal 
occur  in  the  earthy  or  fragmentary  layers,  as  distin- 
guished from  the  pure  coal.  Those  occurring  in  cannel 
coal  are  in  the  same  case,  so  that  the  general  mode  of 
occurrence  implies  water-driftage,  since,  in  the  case  of 
bodies  so  large  and  dense,  wind-driftage  to  great  distances 
would  be  impossible. 

These  facts,  taken  in  connection  with  the  differences 
between  these  macrospores  and  those  of  any  known  land- 
plant  of  the  Palaeozoic,  would  lead  to  the  inference  that 
they  belonged  to  aquatic  plants,  and  these  vastly  abundant 
in  the  waters  of  the  Erian  and  Carboniferous  periods. 

It  is  still  further  to  be  observed  that  they  are  not,  in 
the  Erian  beds,  accompanied  with  any  remains  of  woody 
or  scalariform  tissues,  such  as  might  be  expected  in  con- 
nection with  the  debris  of  terrestrial  acrogens,  and  that, 
on  the  other  hand,  we  find  them  enclosed  in  cellular 
sporocarps,  though  in  the  majority  of  cases  these  liave 
been  removed  by  dehiscence  or  decay. 

These  considerations,  I  think,  all  point  to  the  prob- 
ability which  I  have  suggested  in  my  ])apers  on  this  sub- 
ject referred  to  above,  that  we  have  in  these  objects  the 
organs  of  fructification  of  plants  belonging  to  the  order 
Bhizocarpece,  or  akin  to  it.  The  comparisons  which  I 
have  instituted  with  the  sporocarps  and  macrospores  of 
these  plants  confirm  this  suggestion.      Of  the  modern 


THE  BRIAN   OR  DEVONIAN  FORESTS. 


69 


Bpecies  which  I  have  had  an  opportunity  to  examine, 
Salvinia  natans  of  Europe  perhaps  presents  the  closest 
resemblance.  In  this  plant  groups  of  round  cellular 
sporocarps  appear  at  the  bascv  of  the  floating  fronds. 
They  are  about  a  line  in  diameter  when  mature,  and  are 
of  two  kinds,  one  containing  macrosporcs,  the  other  mi- 
crospores or  antheridia.  The  first,  when  mature,  hold  a 
number  of  closely  packed  globular  or  oval  sporangia  of 
loose  cellular  tissue,  attached  to  a  central  placenta.  Each 
of  these  sporangia  contains  a  single  macrospore,  perfectly 
globular  and  smooth,  with  a  dense  outer  membrane  (ex- 
hibiting traces  of  lamination,  and  showing  within  an 
irregularly  vacuolated  or  cellular  structure,  probably  a 
prothallus).  I  cannot  detect  in  it  the  peculiar  pores 
which  appear  in  the  fossil  specimens.  Each  macrospore 
is  about  one-seventieth  of  an  inch  in  diameter  when  ma- 
ture. The  sporocarps  of  the  microspores  contain  a  vastly 
greater  number  of  minute  sporangia,  about  one  two-hun- 
dredths  of  an  inch  in  diameter.  These  contain  disc-like 
antheridia,  or  microspores  of  very  minute  size. 

The  discs  from  Kettle  Point  and  from  the  Ohio  black 
shale,  and  from  the  shale  boulders  of  the  Chicago  clays, 
are  similar  to  the  macrospores  of  Salvinia,  except  that 
they  have  a  thicker  wall  and  are  a  little  less  in  diameter, 
being  about  one-eightieth  of  an  inch.  The  Brazilian 
sporocarps  are  considerably  larger  than  those  of  the  mod- 
ern Salvinia,  and  the  macrospores  approach  in  size  to 
those  of  the  modern  species,  being  one  seventy-fifth  of  an 
inch  in  diameter.  They  also  seem,  like  the  modern  spe- 
cies, to  have  thinner  walls  than  those  from  Canada,  Ohio, 
and  Chicago.  No  distinct  indication  has  been  observed 
in  the  fossil  species  of  the  inner  Sporangium  of  Salvinia. 
Possibly  it  was  altogether  absent,  but  more  probably  it  is 
not  preserved  as  a  distinct  structure. 

With  reference  to  the  microspores  of  Salvinia,  it  is  to 
be  observed  that  the  sporocarps,  and  the  contained  spores 


li 


Mil 


^^ 


1 

i 
; 

11 

Lt- 

60 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


or  antheridia,  aro  very  delicate  and  destitute  of  the  dense 
outer  wall  of  the  macrospores.  Hence  such  parts  are 
little  likely  to  have  been  preserved  in  a  fossil  state  ;  and 
in  the  Erian  shales,  if  present,  they  probably  appear 
merely  as  flocculcnt  carbonaceous  matter  not  distinctly 
marked,  or  as  minute  granules  not  well  defined,  of  which 
there  arc  great  quantities  in  some  of  the  shales. 

The  vegetation  appertaining  to  the  Sporangites  has 
not  been  distinctly  recognised.  I  have,  however,  found 
in  one  of  the  Brazilian  specimens  two  sporocarps  attached 
to  what  seems  a  fragment  of  a  cellular  frond,  and  numer- 
ous specimens  of  the  supposed  Alga),  named  Sjnrophyloriy 
are  found  in  the  shales,  but  there  is  no  evidence  of  any 
connection  of  this  plant  with  the  Protosalvinia. 

Modern  Rhizocarps  present  considerable  differences  as 
to  their  vegetative  parts.  Some,  like  Pilularia,  have 
simple  linear  leaves  ;  others,  like  Marsilea,  have  leaves  in 
whorls,  and  cuneate  in  form  ;  while  others,  like  Azolla 
and  Salvinia,  have  frondose  leaves,  more  or  less  pinnate 
in  their  arrangement.  If  we  inquire  as  to  fossils  repre- 
senting these  forms  of  vegetation,  we  shall  find  that  some 
of  the  plants  to  be  noticed  in  the  immediate  sequel  may 
have  been  nearly  allied  to  the  Rhizocarps.  In  the  mean 
time  1  may  state  that  I  have  proposed  the  generic  name 
Protosalvinia  for  these  curious  macrospores  and  their 
coverings,  and  have  described  in  the  paper  in  the  "  Bul- 
letin of  the  Chicago  Academy  of  Sciences,"  already 
quoted,  five  species  which  may  be  referred  to  this  genus. 

These  facts  lead  to  inquiries  as  to  the  origin  of  the 
bituminous  matter  which  naturally  escapes  from  the 
rocks  of  the  earth  as  petroleum  and  inflammable  gas,  or 
which  may  be  obtained  from  certain  shales  in  these  forms 
by  distillation.  These  products  are  compounds  of  carbon 
and  hydrogen,  and  may  be  procured  from  recent  vegetable 
substances  by  destructive  distillation.  Some  vegetable 
matters,  also,  are  much  richer  in  carbon  and  hydrogen 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


61 


or 


than  others,  and  it  is  a  remarkable  fact  that  the  spores  of 
certain  cryptogamous  plants  are  of  this  kind,  as  wo  see  iu 
the  inflammable  character  of  the  dry  spores  of  Lycopo- 
dium  ;  and  we  know  that  the  slow  putrefaction  of  such 
material  undergrr  and  effects  chemical  changes  by  which 
bituminous  matter  can  be  produced.  There  is,  there- 
fore, nothing  unreasonable  in  the  supposition  advanced 
by  Prof.  Orton,  that  the  spores  so  abundantly  contained 
in  the  Ohio  black  shales  are  important  or  principal  sources 
of  the  bituminous  matter  which  they  contain.  Micro- 
scopic sections  of  this  shale  show  that  much  of  its  mate- 
rial consists  of  the  rich  bituminous  matter  of  these  spores 
(Fig.  16).  At  the  same  time,  while  we  may  trace  the 
bitumen  of  these  shales,  and  of  some  beds  of  coal,  to  this 
cause,  we  must  bear  in  mind  that  there  are  other  kinds  of 
bituminous  rocks  which  show  no  such  structures,  and  may 
have  derived  their  combustible  material  from  other  kinds 
of  vegetable  matter,  whether  of  marine  or  of  land  plants. 
We  shall  better  understand  this  when  we  have  considered 
the  origin  of  coal. 

The  macrosporcs  above  referred  to  may  have  belonged 
to  humble  aquatic  plants  mantling  the  surfaces  of  water 
or  growing  up  from  the  bottom,  and  presenting  little 
aerial  vegetation.  But  there  are  other  Erian  plants,  as 
already  mentioned,  which,  while  of  higher  structure,  may 
be  of  Rhizocarpean  affinities. 

One  of  these  is  the  beautiful  plant  with  whorls  of 
wedge-shaped  leaves,  to  which  the  name  Sphenophyllum 
(see  Fig.  20)  has  been  given.  Plants  referred  to  this 
genus  have  been  described  by  Lesquereux  from  the  upper 
part  of  the  Siluro-Cambrian,*  and  a  beautiful  little  spe- 
cies occurs  iu  the  Erian  shales  of  St.  John,  New  Bruns- 
wick.f     The  genus  is  also  continued,  and  is  still  more 

*  "  American  Journal  of  Science." 

f  Dawson,  "  Report  on  Devonian  Plants,"  1870. 


62 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


abundant,  in  tlio  Carboniferous.  Many  years  ago  I  ob- 
served, in  a  beautiful  specimen  collected  by  Sir  W.  E. 
Logan,  in  New  Brunswick,  tliat  the  stem  of  this  plant 
had  an  axis  of  reticulated  and  scalariforra  vessels,  and  an 
outer  bark.*  Renault  and  Williamson  have  more  recently 
obtained  more  perfect  specimens,  and  the  former  has 
figured  a  remarkably  complex  triangular  axis,  containing 
punctate  and  barred  vessels,  and  larger  punctate  vessels 
filling  in  its  angles.  Outside  of  this  there  is  a  cellular 
inner  bark,  and  this  is  surrounded  by  a  thick  fibrous  en- 
velope. That  a  structure  so  complex  should  belong  to 
a  plant  so  humble  in  its  aflBnities  is  one  of  the  strange 
anomalies  presented  by  the  old  world,  and  of  which  we 
shall  find  many  similar  instances.  The  fruit  of  Spheno- 
phyllum  was  borne  in  spikes,  with  little  whorls  of  bracts 
or  rudimentary  leaves  bearing  round  sporocarps. 


Fio.  17. — I^tilophijton  jtiumoaum  (Lower  Carboniferous,  Nova  Scotia). 
^Natural  size  and  muguiiied. 

A  second  type  of  plant,  which  may  have  been  Rhizo- 
carpean  in  its  affinities,  is  that  to  which  I  have  given  the 
name  Ptilopliyton.\     It  consists  of  beautiful  feathery 

*  "Journal  of  the  Geological  Society,"  1865. 
f  Flumalina  of  Hall. 


ifi 


THE  ERIAN  PR  DEVONIAN  FORESTS. 


08 


fronds,  apparently  bearing  on  parts  of  tho  main  stem  or 
petiole  small  rounded  sporocarps.  They  are  found  abun- 
dantly in  tho  Middle  Erian  of  tho  State  of  New  York, 
and  also  occur  in  Scotland,  while  one  species  api)ears  to 
occur  in  Nova  Scotia,  as  high  as  the  Lower  Carboniferous 
(Figs.  17,  18). 

These  organisms  have  been  variously  referred  to  Lyco- 
pods,  to  Alga3,  or  to  Zoophytes,  but  an  extended  compari- 


Fio.  18. — Ptilophyfon  TJiomaoni  (Scotland),  a,  Iinprossion  of  plant  in 
vernation,  o,  Branches  conjecturuliy  restored,  c,  Bruuches  of  Zyco- 
podites  Miller i,  on  same  slab. 

son  of  American  and  Scottish  specimens  has  led  me  to 
the  belief  that  they  were  aquatic  plants,  more  likely  to 
have  been  allied  to  Rhizocarps  than  to  any  other  group. 
Some  evidence  of  this  will  be  given  in  a  note  appended 
to  this  chapter. 


Ill 


fr^ 


>iii 


I 


m 


i 


f    r  i 


64 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


4  ! 


ill 


Fio.  19.  —  I^ilopJiyton,  prineeps^  restored 
(Lower  Eriun,  Gaspd).  o,  Fruit,  natural 
sizo.  i,  Stetn.  natunil  size,  c,  Scnlari- 
fonn  tissue  of"  tlio  axis,  lii^r.^ily  magni- 
fied. In  the  restoration,  one  side  is  rcpre- 
Bcatcd  in  vernation  and  the  other  in  fruit. 


Another  genus, 
which  I  have  named 
Psilophyton  *  (Figs. 
19,  2]),  may  be  re- 
garded as  a  connect- 
ing link  between  the 
Rliizocarps  and  the 
Lycopods.  It  is  so 
named  from  its  resem- 
blance, in  some  re- 
spects, to  the  curi- 
ous parasitic  Lycopods 
placed  in  the  modern 
genus  Psilotum.  Sev- 
eral species  have  been 
described,  and  they  are 
eminently  characteris- 
tic of  the  Lower  Bri- 
an, in  which  they 
were  first  discovered 
in  Gasp6.  The  typ- 
ical species,  Psilophy- 
ton princeps,  which 
fills  many  beds  of  shale 
and  sandstone  in  Gas- 
pe  Bay  and  the  head 
of  the  neighbouring 
Bay  des  Chaleurs  with 
its  slender  stems  and 
creeping,  cord-like  rhi- 
zomes, may  be  thus  de- 
scribed : 

Stems     branching 


*  "Journal  of  the  Geological  Society,"  vola.  xv.,  xviii.,  and  xix.,  "Re- 
port on  Devonian  Plants  of  Canada,"  1871. 


THE  ERIAN  OR  DEVONIAN  FORESTS. 


65 


Fio.  20.  —  Sphe- 
iiophyllum  nn- 
tiguHin  (Erian, 
Is'ew  BniiiBwiek), 
See  pp.  61,  C7. 


dichotomously,  and  covered  with  interrupted  ridges. 
Leavoo  rudimentary,  or  short,  rigid,  and  pointed  ;  in 
barren  stems,  numerous  and  spirally  arranged  •  in  fertile 
stems  and  brauchlets,  sparsely  scattered  or  absent ;  in 
decorticated  specimens,  represented  by  a 

minute  punctate  scars.  Young  branch- 
es circinate  ;  rhizomata  cylindrical,  cov- 
ered with  hairs  or  ramenta,  and  having 
circular  areoles  irregularly  disposed,  giv- 
ing origin  to  slender  cylindrical  rootlets. 
Internal  structure* — an  axis  of  scalari- 
form  vessels,  surrounded  by  a  cylinder  of 
parenchymatous  cells,  and  by  an  outer 
cylinder  of  elongated  woody  cells.  Fruc- 
tilication  consisting  of  naked  oval  spore- 
cases,  borne  usually  in  pairs  on  slender, 
curved  pedicels,  either  lateral  or  terminal. 

This  species  was  fully  described  by  me  in  the  papers 
referred  to  above,  from  specimens  obtained  from  the  rich 
exposures  at  Gaspe  Bay,  and  which  enabled  me  to  illus- 
trate its  parts  more  fully,  perhaps,  than  those  of  any 
other  species  of  so  great  antiquity.  In  the  specimens  I 
had  obtained  I  was  able  to  recognise  the  forms  of  the 
rhizomata,  stems,  branches,  and  rudimentary  leaves,  and 
also  the  internal  structure  of  the  stems  and  rhizomata, 
and  to  illustrate  the  remarkable  resemblance  of  tiie  forms 
and  structures  to  those  of  the  modern  Psilnlum.  The 
fructification  was,  however,  altogether  peculiar,  consist- 
ing of  narrowly  ovate  sporangia,  borne  usually  in  pairs, 
on  curvvid  and  apparently  rigid  petioles.  Under  the 
microscope  these  sporangia  show  indications  of  cellular 
structure,  and  appear  to  have  been  membranous  in  char- 
acter. In  some  specimens  dehiscence  appears  to  have 
taken  place  by  a  slit  in  one  side,  and,  clay  having  entered 
into  the  interior,  both  walls  of  the  spore-case  can  be  seen. 
In  other  instances,  being  flattened,  they  might  be  m  "- 


r 


66 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


ll 


f 


taken  for  scales.  No  spores  could  be  observed  in  any  of 
the  specimens,  though  in  some  the  surface  was  marked 
by  slight,  rounded  prominences,  possibly  the  impressions 
of  the  spores  within.     This  peculiar  and  very  simple  style 


;*        I 


Fio.  21. — Lcpidodendron  and  Psilophyton  (Erian,  New  Bnmswick). 
A,  Lepidodendroii  Gaspianuni.    b,  o,  Dsiiophi/ton  elegans, 

of  spore-case  is  also  characteristic  of  other  species,  and 
gives  to  Psilophyton  a  very  distinct  generic  character. 
These  naked  spore-cases  may  be  comj^red  to  those  of 
such   lycopodiaceous  plants  as  Psilotum,  in  which  the 


31 
III 


THE  BRIAN   OB  DEVONIAN  FORESTS. 


67 


scales  are  rudimentary.  They  also  bear  some  resemblance, 
though  on  a  much  larger  scale,  to  the  spore-cases  of  some 
Erian  ferns  {Arclimopteris),  to  be  mentioned  in  the 
sequel.  On  the  whole,  however,  they  seem  most  nearly 
related  to  the  sporocarps  of  the  Rhizocarpea3. 

Arthrostigma,  which  is  found  in  the  same  beds  with 
Psilophyton,  was  a  plant  of  more  robust  growth,  with 
better-developed,  narrow,  and  pointed  leaves,  borne  in  a 
verticillate  or  spiral  manner,  and  bearing  at  the  ends  of 
its  branches  spikes  of  naked  sporocarps,  apparently  simi- 
lar to  those  of  Psilophyton  but  more  rounded  in  form. 
The  two  genera  must  nave  been  nearly  related,  and  the 
slender  branchlets  of  Arthrostigma  are,  unless  well  pre- 
served, scarcely  distinguishable  from  the  stems  of  Psilo- 
phyton.* 

If,  now,  we  compare  the  vegetation  of  these  and  simi- 
lar ancient  plants  with  that  of  modern  Rhizocarps,  we 
shall  find  that  the  latter  still  present,  though  in  a  de- 
pauperated and  diminished  fo^-m,  some  of  the  character- 
istics of  their  predecessors.  Some,  like  Pilularia,  have 
simple  linear  leaves  ;  others,  like  Marsilea,  have  leaves  in 
verticils  and  cuneate  in  form  ;  while  others,  like  Azolla 
and  Salvinia,  have  frondose  leaves,  more  or  less  pinnate 
in  their  arrangement.  The  first  type  presents  little  that 
is  characteristic,  but  there  are  in  the  Erian  sandstones 
and  shales  great  quantities  of  filamentous  and  linear  ob- 
jects which  it  has  been  impossible  to  refer  to  any  genus, 
and  which  might  have  belonged  to  plants  of  the  type  of 
Pilularia.  It  is  quite  possible,  also,  that  such  plants  as 
Psilophyton  glabrum  and  Cordaitcs  angustifolia,  of  which 
the  fructification  is  quite  unknown,  may  have  been  allied 
to  Rhizocarps.  With  regard  to  the  verticillate  type,  we 
are  at  once  reminded  of  Sphenophyllum  (Fig.  20),  which 

*  Reports  of  the  auther  on  "  Devonian  Plants,"  "  Geological  Survey  cf 
Canada,"  which  see  for  details  as  to  Erian  Flora  of  northeaatern  America. 


|l 


n 


:t    = 


ill 


1 1 


i> 


f 


I 


68 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


many  palseo-botanists  have  referred  to  the  MarsiUacm, 
though,  like  other  Palasozoic  Acrogens,  it  presents  com- 
plexities not  seen  in  its  modern  representatives.  S.  pri- 
"ncBVum  of  Lesquere  i?  found  in  the  Hudson  River 
group,  and  my  S.  antiquum  in  the  Middle  Eri.in.  Be- 
sides these,  there  are  in  the  Silurian  and  Erian  beds 
plants  with  verticillate  leaves  which  have  been  placed 
with  the  Annularige,  but  which  may  have  differed  from 
them  in  fructification.  Annularia  laxa,  of  the  Erian, 
and  Protannularia  HarJcnessii,  of  the  Siluro-Cambrian, 
may  be  given  as  examples,  and  must  have  been  aquati«; 
plants,  probably  allied  to  Rhizocarps.  It  is  deserving  of 
notice,  also,  that  the  two  best-known  species  of  Psilophy- 
ton  {P.  princeps  and  P.  rohustius),  while  allied  to  Ly- 
copods  by  the  structure  of  the  stem  and  such  rudimentary 
foliage  as  they  possess,  are  also  allied,  by  the  form  of 
their  fructification,  to  the  Rhizocarps,  and  not  to  ferns, 
as  some  palaeo-botanists  have  incorrectly  supposed.  A 
similar  remark  applies  to  ArthrostUjma  ;  and  the  beautiful 
pinnately  leaved  Ptilnphyton  may  be  taken  to  represent 
that  tyi  e  of  foliage  as  seen  in  modern  Rhizocarps,  while 
the  allied  forms  of  the  Carboniferous  which  Lesquereux 
has  named  Trochophyllum,  seem  to  have  had  sporocarps 
attached  to  the  stem  in  the  manner  of  Azolla. 

The  whole  of  this  evidence,  I  think,  goes  to  show  that 
in  the  Erian  period  there  were  vast  quantities  of  aquatic 
plants,  allied  to  the  modern  Rhizocarps,  and  that  the  so- 
called  Sporangites  referred  to  in  this  paper  were  probably 
the  drifted  sporocarps  and  macrospores  of  some  of  these 
plants,  or  of  plants  allied  to  them  in  structure  ard  habit, 
of  which  the  vegetative  organs  have  perished.  I  have 
shown  that  in  the  Erian  period  there  were  vast  swampy 
flats  covered  with  Psilopliyton,  and  in  similar  submerged 
tracts  near  to  the  sea  the  Protosalvinia  may  have  filled 
the  waters  and  have  given  off  the  vast  multitudes  of 
macrospores  which,  drifted  by  currents,  have  settled  in  the 


THE  BRIAN  OR   DEVONIAN  FORESTS. 


69 


mud  of  the  black  shales.  "We  have  thus  a  remarkable 
example  c?  a  group  of  plants  reduced  in  modern  times  to 
a  few  insignificant  forms,  but  which  played  a  great  role  in 
the  ancient  Palaeozoic  world. 

Leaving  the  Rhizocarps,  we  may  now  turn  to  certain 
other  families  of  Erian  plants.  The  first  to  attract  our 
attention  in  this  age  would  naturally  be  the  Lycopods, 
the  club-mosses  or  ground-pines,  which  in  Canada  and 
the  Eastern  States  carpet  the  ground  in  many  parts  of 
our  woods,  and  are  so  available  for  the  winter  decoration 
of  our  houses  and  public  buildings.  If  we  fancy  one  of 
these  humble  but  graceful  plants  enlarged  to  the  dimen- 
Bions  of  a  tree,  we  shall  have  an  idea  of  a  Lepidodendron, 
or  of  any  of  its  allies  (Figs.  15,  31).  These  large  lycopo- 
diaceous  trees,  which  in  different  specific  and  generic 
forms  were  probably  dominant  in  the  Erian  woods,  re- 
sembled in  general  those  of  modern  times  in  their  fruit 
and  foliage,  except  that  their  cones  were  large,  and  prob- 
ably in  most  cases  with  two  kinds  of  spores,  and  their 
leaves  were  also  often  very  long,  thus  bearing  a  due  pro- 
portion to  the  trees  which  they  clothed.  Their  thick 
stems  required,  however,  more  strength  than  is  necessary 
in  their  diminutive  successors,  and  to  meet  this  want 
some  remarkable  structures  were  introduced  similar  to 
those  now  found  only  in  the  stems  of  i)lants  of  higher 
rank.  The  cells  and  vessels  of  all  plants  consist  of  thin 
walls  of  woody  matter,  enclosing  the  sap  and  other  con- 
tents of  these  sacs  and  tubes,  and  when  strength  is  re- 
quired it  is  obtained  by  lining  their  interior  with  suc- 
cessive coats  of  the  hardest  form  of  woody  matter,  ii.iually 
known  as  lignin.  But  while  the  walls  remain  thin,  they 
afford  free  passage  to  the  sap  to  nourish  every  part.  If 
thickened  all  over,  they  would  become  impervious  to  sap, 
and  therefore  unsuited  to  one  of  their  most  important 
functions.  These  two  ends  of  strength  and  permeability 
are  secured  by  partial  linings  of  lignin,  leaving  portions  of 
8 


'■':MlH 


n, 

f 
I  1 

I 


TO 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


the  original  wall  uncovered.     But  this  may  be  done  in  a 
great  variety  of  ways. 

The  most  ancient  of  these  contrivances,  and  one  still 
continued  in  the  world  of  plants,  is  that  of  the  barred 
or  scalariform  vessel.  This  may  be  either  square  or  hex- 
agonal, so  as  to  admit  of  being  packed  without  leaving 
vacancies.  It  is  strengthened  by  a  thick  bar  of  ligneous 
matter  up  each  angle,  and  these  are  connected  by  cross- 
bars so  as  to  form  a  framework  resembling  several  ladders 
fastened  together.  Hence  the  name  scalariform,  or  lad- 
der-like. Now,  in  a  modern  Lycopod  there  is  a  central 
axis  of  such  barred  vessels  associated  with  simpler  fibres 
or  elongated  cells.  Even  in  Sphenopliyllwn  and  Psilo- 
pTiyton,  already  referred  to  as  allied  to  Rhizocarps,*  there 
is  such  a  central  axis,  and  in  the  former  rigidity  is  given 
to  this  by  the  vascular  and  woody  elements  being  ar- 
ranged in  the  form  of  a  three-sided  prism  or  three-rayed 
star.  But  such  arrangements  would  not  suffice  for  a  tree, 
and  hence  in  the  arboreal  Lycopods  of  the  Erian  age  a 
more  complex  structure  is  introduced.  The  barred  ves- 
sels were  expanded  in  the  first  instance  into  a  hollow 
cylinder  filled  in  with  pith  or  cellular  tissue,  and  the 
outer  rind  was  strengthened  with  greatly  thickened  cells. 
But  even  this  was  not  sufficient,  and  in  the  older  stems 
wedge-shaped  bundles  of  barred  tissue  were  run  out  from 
the  interior,  iorming  an  external  woody  cylinder,  and  in- 
side of  the  rind  were  placed  bundles  of  tough  bast  fibres. 
Thus,  a  stem  was  constructed  having  pith,  wood,  and 
bark,  and  capable  of  additions  to  the  exterior  of  the 
woody  wedges  by  a  true  exogenous  growth.  The  plan  is, 
in  short,  the  same  with  that  of  the  stems  of  the  exogenous 
trees  of  modern  times,  except  that  the  tissues  employed 
are  less  complicated.     The  structures  of  these  remarkable 

*  First  noticed  by  the  author,  "Journal  of  Geological  Society,"  1866; 
but  more  completely  by  Renault,  "  Comptes  Rendus,"  1870. 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


74 


trees,  and  the  manner  in  which  they  anticipate  those  of 
the  true  exogens  of  modern  times,  have  been  admirably 
illustrated  by  Dr.  Williamson,  of  Manchester.  His 
papers,  it  is  true,  refer  to  these  plants  as  existing  in  the 
Carboniferous  age,  but  there  is  every  reason  to  believe 
that  they  were  of  the  same  character  in  the  Erian.  The 
plan  is  the  same  with  that  now  seen  in  the  stems  of  exoge- 
nous phaenogams,  and  which  has  long  ceased  to  be  used 
in  those  of  the  Lycopods.  In  this  way,  however,  large 
and  graceful  lycopodiaceous  trees  were  constructed  in  the 
Erian  period,  and  constituted  the  staple  of  its  forests. 

The  roots  of  these  trees  were  equally  remarkable  with 
their  stems,  and  so  dissimilar  to  any  now  existing  that 
botanists  were  long  disposed  to  regard  them  as  inde- 
pendent plants  rather  than  roots.  They  were  similar  in 
general  structure  to  the  stems  to  which  they  belonged, 
but  are  remarkable  for  branching  in  a  very  regular  man- 
ner by  bifurcation  like  the  stems  above,  and  for  the  fact 
that  their  long,  cylindrical  rootlets  were  arranged  in  a 
spiral  manner  and  distinctly  articulated  to  the  root  after 
the  manner  of  leaves  rather  than  of  rootlets,  and  fitting 
them  for  growing  in  homogeneous  mud  or  vegetable 
muck  They  are  the  so-called  Stigmaria  roots,  which, 
though  found  in  the  Erian  and  belonging  to  its  lycopo- 
diaceous plants,  attained  to  far  greater  importance  in  the 
Carboniferous  period,  where  we  shall  meet  with  them  again. 

There  were  different  types  of  lycopodiaceous  plants 
in  the  Erian.  In  addition  to  humble  Lycopods  like  those 
of  our  modern  woods  and  great  Lepidodendra,  which  were 
exaggerated  Lycopods,  there  were  thick-stemmed  and  less 
graceful  species  with  broad  rhombic  scars  (Leptophleum), 
and  others  with  the  leaf-scars  in  vertical  rows  {Sigillaria), 
and  others,  again,  with  rounded  leaf-scars,  looking  like 
the  marks  on  Stigmaria,  and  belonging  to  the  genus 
Cyclostigma.  Thus  some  variety  was  given  to  the  arbo- 
real club-mosses  of  these  early  forests.     (See  Fig.  15.) 


5>^ 


72  THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


Another  group  of  plants  which 
attained  to  great  development  in 
the  Erian  age  is  that  of  the  Ferns 
or  Brackens.  The  oldest  of  these 
yet  known  are  found  in  the  Mid- 
dle Erian.  The  Eopteris  of  Sa- 
porta,  from  the  Silurian,  at  one 
time  supposed  to  carry  this  type 
much  further  back,  has  unfortu- 
nately been  found  to  be  a  mere 
imitative  form,  consisting  of 
films  of  pyrites  of  leaf -like  shapes, 
and  produced  by  crystallisation. 
In  the  Middle  Erian,  however, 
more  especially  in  North  Ameri- 
ca, many  species  have  been  found 
(Figs.  32  to  24).*  I  have  myself 
recorded  more  than  thirty  spe- 
cies from  the  Middle  Erian  of 
Canada,  and  these  belong  to  sev- 
eral of  the  genera  found  in  the 
Carboniferous,  though  some  are 
peculiar  to  the  Erian.  Of  the 
latter,  the  best  known  are  per- 
haps those  of  the  genus  ArchcB- 
opteris  (Fig.  24),  do  abundant 
in  the  plant-beds  of  Kiltorcan 
in  Ireland,  as  well  as  in  North 
America.  In  this  genus  the 
fronds  are  large  and  luxuriant, 
with  broad  obovate  pinnules  de- 
current  on  the  leaf-stalk,  and 
with  simple  sac-like  spore-cases 
borne  on  modified  pinnae.  An- 
other very  beautiful  fern  found 


Fio.  2'2.— Erian  ferns  ([New 
Brunswick),  a,  Aneimitea 
obtusa.  0,  Neuroi)teris  poly- 
morpha.  f,  Sphenopteris 
pilosa.  N,  Hymenophyllites 
subfurcatua. 


*  For  descriptions  of  these  ferns,  see  reports  cited  above. 


TOE  BRIAN  OR  DEVONLvN   FORESTS. 


T8 


Fio.  23. — Erian  ferns  (New  Brunswick),  b,  Cyclopteris  valida,  and 
pinnule  enlarged,  n,  Sphenopteris  marginata^  and  portion  en'.arf^ed. 
B,  Sphenopteris  Ilartii,  ci,  Hijmehopkj/llites  curtilonus.  n,  Hi/meno- 
phyUites  (fersdarjfii,  and  portion  enlarged,  i,  Alethopteris  discrepaiis, 
K,  Pecopteris  serr'ulaia.    ^,  Fecopteris  preciosa.    a,  J  Idhopteris  Ferleyi. 


I 


74 


TUE  GEOLOGICAL  HISTORY  OF  PLANTS. 


; 


with  ArchcBopteris  is  that  which  I  have  named  Platyphyl- 
lum,  and  which  grew  on  a  creeping  stem  or  parasitically 
on  stems  of  other  i)lants,  and  had  marginal  fructification.* 


Fio.  24. — Archcpopteris  Jacksoni,  Dawson  (Maine).     An  Upper  Erian 
fern,    a,  6,  Pinnules  sliowing  venation. 

*  "  Reports  on  Fossil  Plants  of  the  Devonian  and  Upper  Silurian  of 
Canada,"  1871,  &c. 


L 


THE   BRIAN  OR  DEVONIAN  FORESTS. 


75 


Another  very  remarkable  fern,  wlilch  some  botanists  have 
supposed  may  belong  to  a  higher  group  than  the  ferns,  is 
Megalopteris  (Fig.  2G). 

Some  of  the  Erian  ferns  attained  to  the  dimensions  of 
tree-ferns.  Large  stems  of  these,  which  must  have  floated 
out  far  from  land,  have  been  found  by  Newberry  in  the 
marine  limestone  of  Ohio  {Caulopteris  antiqua  and  C. 
peregrina,  Newberry),*  and  Prof.  Hall  has  found  in  the 


Fig.  25. — An  Erian  tree-fern.     Caulopteris  Lochvoodi^  Dawson, 
reduced.     (From  a  specimen  from  Gilboa,  New  \ork.) 

Upper  Devonian  of  Gilboa,  New  York,  the  remains  of  a 
forest  of  tree-ferns  standing  in  situ  with  their  great 
masses  of  aerial  roots  attached  to  the  soil  in  which  they 
grew  {Caulopteris  LocTciuoodi,  Dn.).f 

These  aerial  roots  introduce  us  to  a  new  contrivance 
for  strengthening  the  stems  of  plants  by  sending  out  into 
the  soil  multitudes  of  cord-like  cylindrical  roots  from 


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*  "Journal  of  the  Geological  Society,"  1811. 


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76 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 

f 


various  heights  on  the  stem,  and  which  form  a  series  of 
stays  like  the  cordage  of  a  ship.     This  method  of  support 


FiQ.  2Q.—Me(falopteri8  Dawsoni,  Ilartt  (Erian,  New  Brunswick),  rt,  Frag- 
ment  of  pinna,  h,  Point  of  pinnule,  c,  Venation.  (Tlie  midrib  is  not 
accurately  given  in  this  figure.) 

still  continues  in  the  modern  tree-ferns  of  the  tropics 
and  the  southern  hemisphere.     In  one  kind  of  tree-fern 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


77 


stem  from  the  Erian  of  New  York,  there  is  also  a  special 
arrangement  for  support,  consisting  of  a  series  of  pecul- 
iarly arranged  radiating  plates  ^'f  scalariform  vessels,  not 
exactly  like  those  of  an  exogenous  stem,  but  doing  duty 
for  it  {A  steropteris).* 
Similar  plants  have 
been  described  from 
the  Erian  of  Falken- 
berg,  in  Germany, 
and  of  Saalfeld,  in 
Thuringia,  by  Goep- 
pert  and  linger,  and 
are  referred  to  ferns 
by  the  former,  but 
treated  as  doubtful 
by  the  latter,  f  This 
peculiar  type  of  tree- 
fern  is  apparently  a 
precursor  of  the  more 
exogenous  type  of 
Heterangium,  recent- 
ly described  and  re- 
ferred to  ferns  by 
Williamson.  Here, 
again,  we  have  a  me- 
chanical contrivance 
now  restricted  to 
higher  plants  appro- 
priated by  these  old 
cryptogams. 

The  history  of  the  ferns  in  geological  time  is  remark- 
ably different  from  that  of  the  Lycopods  ;  for  while  the 

*  "Journal  of  the  Geological  Society,"  London,  1881. 

t  "  Sphenopteris  Refracta,"  Goeppert ;  "  Flora  des  Uebcrgangsge- 
birses."  "  Cladoxylon  Mirabilc,"  Unger ;  '*  Palseontologie  des  Thuringer 
Waldes." 


Fio.  27. — Calamites  radiatus  (Erian,  New 
Brunswick). 


I'    1 


lii 


i 

li! 


ti 


78 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


latter  have  long  ago  descended  from  their  pristine  emi- 
nence to  a  very  humble  place  in  nature,  the  former  still, 
in  the  southern  hemisphere  at  least,  retain  their  arboreal 

dimensions  and  an- 
B  ^1^  cient  dominance. 

Cil!k.  The    family   of 

the  Equisetacem,  or 
mare's-tails,  was  also 
represented  by  large 
species  of  Calamites 
and  by  Asterophyl- 
lites  in  the  Erian ; 
but,  as  its  headquar- 
ters are  in  the  Car- 
boniferous, we  may 
defer  its  considera- 
tion till  the  next 
chapter.  (Figs.  27, 
28.) 

Passi  ng  over  these 
for  the  present,  we 
find  that  the  flower- 
ing plants  are  repre- 
sent d  in  the  Eria,n 
forests  by  at  least 
two  types  of  Gym- 
nosperms,  that  of 
Taxincm  or  yews, 
and  an  extinct  family,  that  of  tlio  Cordaites  (Figs.  30,  31). 
The  yew-trees  are  closely  allied  to  the  pines  and  spruces, 
and  are  often  included  with  them  in  the  family  of  Coniferce. 
They  differ,  however,  in  the  habit  of  producing  berries  or 
drupe-like  fruits  instead  of  cones,  and  there  is  some 
reason  to  believe  that  this  was  the  habit  of  the  Erian 
trees  of  this  group,  though  their  wood  in  some  in- 
stances resembles  rather  that  of  the  Araucaria,  or  Nor- 


Fio.  28. — AsterophylUtes  (Erian,  New  Bruns- 
wick). A,  Asterophyllites  latifoUa.  b,  Do,, 
apex  of  stem  {\)  fruit,  c,  c)>,  A.  scutigem. 
D,  A.  latifoha,  larijer  wliorl  of  loavea. 
d's  Loaf.  •"       '        ^ 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


79 


folk  Island  pine,  than  that  of  the  modern  yews.  These 
trees  are  chiefly  known  to  us  by  their  mineralised  trunks, 
which  are  often  found  like  drift-wood  on  modern  sand- 
banks embedded  in  the  Erian  sandstones  or  limestones. 
It  often  shows  its  structure  in  the  most  perfect  man- 
ner in  specimens  penetrated  by  calcite  or  silica,  or  by 
pyrite,   and  in   which   the   original   woody   matter  has 


V 


Fio.  29. — Dadoxylon  Ouangondianum,  an  Erian  conifer,  a.  Frngraent 
Bhowinjr  Sternberfria  pi^li  and  wood:  a,  naedullary  slieatli;  ft,  pith^ 
c,  wood ;  d.  section  of  pith,  b,  Wood-cell ;  a,  hexatronal  areola  | 
i,  pore,  c,  Lonj,'itudinal  section  of  wood,  showinj^,  a,  areolation,  and 
b,  medullary  rays,  d.  Transverse  section,  sliowintr,  a,  wood-cells,  and 
6,  limit  of  layer  of  growth,     (b,  c,  u,  highly  magnified.) 

been  resolved  into  anthracite  or  even  into  graphite. 
These  trees  have  true  woody  tissues  presenting  that  beau- 
tiful arrangement  of  pores  or  thin  parts  enclosed  in  cup- 
iike  discs,  which  is  characteristic  of  the  coniferous  trees, 
and  which  is  a  great  improvement  on  the  barred  tissue 
already  referred  to,  affording  a  far  more  strong,  tough. 


m 


I> 


\ . 


»si  1 


! 


80 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


and  durable  wood,  such  as  we  have  iu  our  modern  pines 
and  yews  (Fig.  29). 

These  primitive  pines  make  their  appearance  in  the 
Middle  Brian,  in  various  parts  of  America,  as  well  as  in 
Scotland  and  Germany,  and  they  are  represented  by  wood 
indicating  the  presence  of  several  species.  I  have  myself 
indicated  and  described  five  species  from  the  Erian  of 
Canada  and  the  United  States.  From  the  fact  that  these 
trees  are  represented  by  drifted  trunks  embedded  in  sand- 
stones and  marine  limestones,  we  may,  perhaps,  infer  that 
they  grew  on  the  rising  grounds  of  the  Erian  land,  and 
that  their  trunks  were  carried  by  river-floods  into  the  sea. 
No  instance  has  yet  certainly  occurred  of  the  discovery  of 
their  foliage  or  fruit,  though  there  are  some  fan-shaped 
leaves  usually  regarded  as  ferns  which  may  have  belonged 
to  such  trees.  These  in  that  case  would  have  resembled 
the  modern  GingTco  of  China,  and  some  of  the  fruits  re- 
ferred to  the  genus  Cardiocarpum  may  have  been  pro- 
duced by  them.  Various  names  have  been  given  to  these 
trees.  I  have  preferred  that  given  by  linger,  Dadoxylon, 
as  being  more  non-committal  as  to  affinities  than  the 
others.*  Many  of  these  trees  had  very  long  internal 
pith-cylinders,  with  curious  transverse  tubulae,  and  which, 
when  preserved  separately,  have  been  named  Sternhergia. 

Allied  to  these  trees,  and  perhaps  intermediate  between 
them  and  the  Cycads,  were  those  known  as  Cordaites 
(Fig.  30),  which  had  trunks  resembling  those  of  Dadoxy- 
lon, but  with  still  larger  Sternhergia  piths  and  an  internal 
axis  of  scalariform  vessels,  surrounded  by  a  comparatively 
thin  woody  cylinder.  Some  of  them  have  leaves  over  a 
foot  in  length,  reminding  one  of  the  leaves  of  broad-leaved 
grasses  or  iridaceous  pi  ts.  Yet  their  flowers  and  fruit 
seem  to  have  been  more  nearly  allied  to  the  yews  than  to 
any  other  plants  (Fig.  31).     Their  stems  were  less  woody 

*  Araucaritca,  Goeppert ;  Arattearioxi/lon,  Kraus. 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


81 


and  their  piths  hirger  than  in  the  true  pines,  and  some 
of  the  larger-leaved  species  must  have  had  thick,  stiff 
branches.  They  are  regarded  as  constituting  a  separate 
family,  intermediate  between  pines  and  cycads,  and,  bc- 


Fio.  30. — Cordaites  Rohhii  (Erian,  New  Brunswick),     or,  Group  of  young 
leaves,    i,  Point  of  leaf.     <•,  Base  of  leaf     rf,  Venation,  magnified. 

ginning  in  the  Middle  Devonian,  they  terminate  in  the 
Permian,  where,  however,  some  of  the  most  gigantic  spe- 
cies occur.  In  so  far  as  the  form  and  structure  of  tlie 
leaves,  stems,  and  fruit  are  concerned,  there  is  marvel- 
lously little  difference  between  the  species  found  in  the 
9 


82 


THE  GEOLOGICAL   HISTORY  OF  PLANTS, 


Erian  and  the  Permian.  They  culminated,  however,  in 
the  Carboniferous  period,  and  the  coal-fields  of  southern 
France  have  proved  so  far  the  richest  in  their  remains. 

Lastly,  a  single  specimen,  collected  by  Prof.  James 
Hall,  of  Albany,  at  Eighteen-mile  Creek,  Lake  Erie,  has 
the  structure  of  an  ordinary  angiospermous  exogen,  and 
has   been  described  by  me  as  Syringoxylon  mirahile* 


Fio.  81. — Erian  fruits,  &c.,  some  wymnospcnnous,  and  probably  of  Cordaites 
and  Taxine  trees  (St.  John,  J^ew  BrunsAvick).  a,  (Jnrdvocarpum  cor- 
nutum.  B,  Cardiocarpum  acutum.  o,  Cardiocarpum  Crampii.  d,  Car- 
diocarpum  £aile>/i.    e,  Trigonocarpum  racemosum.    e>,  e",  Fruits  en- 


o,  Anmtlaria  acuminata. 


larfTcd.     F,  Antliolithes  Deco'  icttg, 

terophyllitea    aeiculark.      n>    Fruit  of  the  same,     k 

{i  young  of  A.),    l,  Pinnul     ia  dispalaiis  (probably  a  root) 


H,  As- 
Cardiocarpum 


This  unique  example  is  sufficient  to  establish  the  fact  of 
the  existence  of  such  plants  at  this  early  date,  unless  some 
accident  may  have  carried  a  specimen  from  a  later  forma- 


*  « 


Journal  of  the  Geological  Society,"  vol.  xviii. 


THE  BRIAN  OR   DEVONIAN  FORESTS. 


83 


tion  to  be  mixed  with  Erian  fossils.  It  is  to  be  observed, 
however,  that  the  non-occurrence  of  any  similar  wood  in 
all  the  formations  between  the  Upper  Erian  and  the  Mid- 
dle Cretaceous  suggests  very  grave  doubt  as  to  the  authen- 
ticity of  the  specimen.  I  record  the  fact,  waiting  further 
discoveries  to  confirm  it.  Of  the  character  of  the  speci- 
men which  I  have  described  I  entertain  no  doubt. 

We  shall  be  better  able  to  realise  the  significance  and 
relations  of  this  ancient  flora  when  we  have  studied  that 
of  the  succeeding  Carboniferous.  We  may  merely  remark 
here  on  the  fact  that,  in  these  forests  of  the  Devonian 
and  in  the  marshes  on  their  margins,  we  find  a  wonder- 
ful expansion  of  the  now  modest  groups  of  llhizocarps 
and  Lycopods,  and  that  the  flora  as  a  whole  belongs  to 
the  highest  group  of  Cryptogams  and  the  lowest  of  Phae- 
nogams,  so  that  it  has  about  it  a  remarkable  aspect  of 
mediocrity.  Further,  while  there  is  evidence  of  some 
variety  of  station,  there  is  also  evidence  of  much  equality 
of  climate,  and  of  a  condition  of  things  more  resembling 
that  of  the  insular  climates  of  the  temperate  portions  of 
the  southern  hemisphere  than  that  of  North  America  or 
Europe  at  present. 

The  only  animal  inhabitants  of  these  Devonian  woods, 
so  far  as  known,  were  a  few  species  of  insects,  discovered 
by  Hartt  in  New  Brunswick,  and  described  by  Dr.  Scud- 
der.  Since,  however,  we  now  know  that  scorpions  as 
well  as  insects  existed  in  the  Silurian,  it  is  probable  that 
these  also  occurred  in  the  Erian,  though  their  remains 
have  not  yet  been  discovered.  All  the  known  insects  of 
the  Erian  woods  are  allies  of  the  shad-flies  and  grasshop- 
pers {Neuroptera  and  Orthopterd),  or  intermediate  be- 
tween the  two.  It  is  probable  that  the  larvae  of  most  of 
them  lived  in  water  and  fed  upon  the  abundant  vegetable 
matter  there,  or  on  the  numerous  minute  crustaceans  and 
worms.  There  were  no  land  vertebrates,  so  far  as  known, 
but  there  were  fishes  {Dipterus,  etc.),  allied  to  the  mod- 


84 


THE   GEOLOGICAL   HISTORY  OF  PLANTS. 


eni  Barramunda  or  Ceratodus  of  Australia,  and  with 
teeth  suited  for  grinding  vegetable  food.  It  is  also  possi- 
ble that  some  of  the  smaller  plate-covered  fishes  (Placo- 
ganoids,  like  PterichtJn/s)  might  have  fed  on  vegetable 
matter,  and,  in  any  case,  if  they  fed  on  lower  animals,  the 
latter  must  have  subsisted  on  plants.  I  mention  these 
facts  to  show  that  the  superabundant  vegetation  of  this 
age,  whether  aquatic  or  terrestrial,  was  not  wholly  useless 
to  animals.  It  is  quite  likely,  also,  that  we  have  yet 
much  to  learn  of  the  animal  life  of  the  Erian  swamps  and 
woods. 


NOTES  TO  CHAPTER  III. 

I. — Classification  of  Spoban'gites. 

It  is,  of  course,  very  unsatisfactory  to  give  names  to  mere  frag- 
ments of  plants,  yet  it  seems  very  desirable  to  have  some  means  of 
arranging  them.  With  respect  to  the  organisms  described  above, 
which  were  originally  called  by  me  Sporangites,  under  the  sup- 
position that  they  were  Sporangia  rather  than  spores,  this  name 
has  so  far  been  vindicated  by  the  discovery  of  the  spore-cases  belong- 
ing to  them,  so  that  I  think  it  may  still  be  retained  as  a  provisional 
name;  but  I  would  designate  the  whole  a,s  Protosalviniw,  meaning 
thereby  plants  with  rhizocarpean  affinities,  though  possibly  when 
better  understood  belonging  to  different  genera.  We  may  under 
these  names  speak  of  their  detached  discs  as  macrospores  and  of 
their  cellular  envelopes  as  sporocarps.  The  following  may  be  recog- 
nized as  distinct  forms : 

1.  Protosalviiiia  Huronensis,  Dawson,  Syn.,  Sporangites  Iluron- 
ensts,  "  Report  on  Erian  Flora  of  Canada,"  1871. — Macrospores,  in 
the  form  of  discs  or  globes,  smooth  and  thick-walled,  the  walls  pene- 
trated by  minute  radiating  pores.  Diameter  about  one  one-hun- 
dredth of  an  inch,  or  a  little  more.  When  m  situ  several  macro- 
spores are  contained  in  a  thin  cellular  sporoearp,  probably  globular 
in  form.  From  the  Upper  Erian,  and  perhaps  Lower  Carboniferous 
shales  of  Kettle  Point,  Lake  Huron,  of  various  places  in  the  State  of 
Ohio,  and  in  the  shale  boulders  of  the  boulder  clay  of  Chicago  and 
vicinity.    First  collected  at  Kettle  Point  by  Sir  W.  E.  Logan,  and 


1 


TUE  BRIAN   OR  DEVONIAN  FORESTS. 


85 


in  Ohio  by  Prof.  Edward  Orton,  and  at  Chicago  by  Dr.  IT.  A.  John- 
son and  Mr.  B.  W.  Thoina.s,  also  in  New  Yorlt  by  Prof.  J.  M.  Clarke. 

The  inacrospores  collected  l)y  Mr.  Thomas  from  the  Chicago 
clays  and  shales  conform  closely  to  those  ot  Kettle  Point,  and  prol)- 
ably  belong  to  the  same  species.  Some  of  them  are  thicker  in  the 
outer  wall,  and  show  the  pores  much  more  distinctly.  These  have 
been  called  by  Mr.  Thomas  »S'.  Chicagoennin,  and  n>ay  be  regarded  as 
a  varietal  form.  Specimens  isolated  from  the  shale  and  mounted 
dry,  show  what  seems  to  have  been  the  hilum  or  scur  of  attachment 
better  than  those  in  balsam. 

Sections  of  the  Kettle  Point  shale  show,  in  addition  to  the  ma- 
crospores,  wider  and  thinner  shreds  of  vegetable  matter,  which  I  am 
inclined  to  suppose  to  be  remains  of  the  sporocarps. 

2.  Protosalvinia  (SporangUesJ  Braziliensis,  Dawson, "  Canadian 
Record  of  Science,"  1883. — Macrospores,  round,  smooth,  a  little 
longer  than  those  of  the  last  species,  or  about  one  seventy-fifth  of 
an  inch  in  diameter,  enclosed  in  round,  oval,  or  slightly  renifonn 
sporocarps,  each  containing  from  four  to  twenty-four  macrospores. 
Longest  diameter  of  sporocarps  tliree  to  six  millimetres.  Structure 
of  wall  of  sporocarps  hexagonal  cellular.  Some  sporocarps  show  no 
macrospores,  and  may  possibly  contain  microspores.  The  specimens 
are  from  the  Erian  of  Brazil.  Discovered  by  Mr.  Orville  Derby. 
The  formation,  according  to  Mr.  Derby,  consists  of  black  shales  be- 
low, about  three  hundred  feet  thick,  and  containing  the  fucoid  known 
as  Spirophyton,  and  probably  decomposed  vegetable  matter.  Above 
this  is  chocolate  and  reddish  shale,  in  which  the  well-preserved  speci- 
mens of  Pi-otosalvinia  occur.  These  beds  are  very  widely  distributed, 
and  abound  in  Protosalvinia  and  Spirophyton. 

3.  Protosalvinia  (Sporangites)  bilobata,  Dawson,  "Canadian 
Record  of  Science,"  1883. — Sporocarps,  oval  or  reniform,  three 
to  six  millimetres  in  diameter,  each  showing  two  rounded 
prominences  at  the  ends,  with  a  depression  in  the  middle,  and 
sometimes  a  raised  neck  or  isthmus  at  one  side  connecting  the 
prominences.  Structure  of  sporocarp  cellular.  Some  of  the  speci- 
mens indicate  that  each  prominence  or  tubercle  contained  several 
macrospores.  At  first  sight  it  would  be  easy  to  mistake  these  bodies 
for  valves  of  Beyrichia. 

Found  in  the  same  formations  with  the  last  species,  though,  in  so 
far  as  the  specimens  indicate^  not  precisely  in  the  same  beds.  Col- 
lected by  Mr.  Derby. 

4.  P-otosalvinia  Clarkei,  Dawson,  P.  bilobata,  Clarke, "  American 
Journal  of  Science." — Macrospores  two-thirds  to  one  millimetre  in 


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66 


TUE  GEOLOGICAL   HISTORY  OF  PLANTS. 


diameter.  One,  two,  or  three  contained  in  enoh  sporoearp,  which  is 
cellular.  The  macroaporcs  have  very  thick  walls  with  radiating  tor- 
tuous tubes.  Unless  this  structure  is  a  result  of  mineral  crystallisa- 
tion, these  macrospores  must  have  had  very  thick  walls  and  must  have 
resemlled  in  structure  the  thickened  cells  of  stone  fruits  and  of  the 
core  of  the  pear,  or  the  tests  of  the  Silurian  and  Erian  seeds  known 
as  Pachytheca,  though  on  a  smaller  scale. 

It  is  to  bo  observed  that  bodies  similar  to  these  occur  in  the  Bog- 
head earthy  bitumen,  and  have  been  described  by  Credner. 

I  have  found  similar  bodies  in  the  so-called  "  Stellar  coal  "  of  the 
coal  district  of  Pictou,  Nova  Scotia,  some  layers  of  which  are  filled 
with  them.  Tiiey  occur  in  groups  or  patches,  which  seem  to  be  en- 
closed in  a  smooth  and  thin  membrane  or  sporocarp.  It  is  quite 
likely  that  these  bodies  are  generically  distinct  from  Protosalvinia. 

5.  Protosalmiia  punctata,  Newton,  "  Geological  Magazine,"  New 
Series,  December  2d,  vol.  ii, — Mr.  Newton  'is  named  the  discs 
found  in  the  white  coal  and  Tiusmanite,  Tasmanites,  the  species  be- 
ing Tasmanites  pnnctatus,  but  as  my  name  Sporangites  had  priority, 
I  do  not  think  it  necessary  to  adopt  this  term,  though  there  can  be 
little  doubt  that  these  organisms  are  of  similar  character.  The  same 
remark  may  be  made  with  reference  to  the  bodies  described  by  Hux- 
ley and  Newton  as  occurring  in  the  Better-bed  coal. 

In  Witham's  "Internal  Structure  of  Fossil  Vegetables,"  1833, 
Plate  XI,  are  figures  of  Lancashire  cannel  which  shows  Sporangites  of 
the  type  of  those  in  the  Erian  shales.  Quckett,  in  his  "  Report  on  the 
Torbane  Hill  Mineral,"  1854,  has  very  well  figured  similar  structures 
from  the  Methel  coal  and  the  Lesmahagow  cannel  coal.  These  are 
the  earliest  publications  on  the  subject  known  to  me ;  and  Quekett, 
though  not  understanding  the  nature  of  the  bodies  he  observed, 
holds  that  they  are  a  usual  ingredient  in  cannel  coals. 

II. — The  Nature  and  Affinities  of  Ptilophyton. 

{Lycopodites  Vanuxemii  of  "  Report  on  Devonian  and  Upper 
Silurian  Plants,"  Part  I.,  page  35.  L.  plumula  of  "  Report  on  Lower 
Carboniferous  Plants,"  page  24,  Plate  I.,  Figs.  7,  8,  9.)  In  the  re- 
ports above  referred  to,  these  remarkable  pinnate,  frond-like  objects 
were  referred  to  the  genus  Lycopodites,  as  had  been  done  by  Goep- 
pert  in  his  description  of  the  European  species  Lycopodites  pennce- 
formis,  which  is  very  near  to  the  American  Erian  form.  Since  1871, 
however,  there  have  been  many  new  specimens  obtained,  and  very 
various  opinions  expressed  as  to  their  affinities.  While  Hall  has 
named  some  of  them  Plumalina,  and  has  regarded  them  as  animal 


--i: 


THE   ERIAN   OR  DEVONIAN   FORESTS. 


87 


V 


structures,  allied  to  hydroids,  Lesquereux  has  dcscriborl  some  of  the 
Carboniferous  forms  under  the  generic  name  2'rorhnphi/llum,  which 
is,  however,  more  appropriate  to  plants  with  vertieillate  leaves  which 
are  included  in  this  genus.  Before  I  had  seen  the  publications  of 
Hall  and  Lesquereux  on  the  subject,  I  had  in  a  paper  on  "Scottish 
Devonian  Plants  "  *  separated  this  group  from  the  genus  Lycopodites, 
and  formed  for  it  the  genus  Ptilophyton,  in  allusion  to  th(>  feather- 
like aspect  of  th(!  species.  My  reasons  for  this,  and  my  present  in- 
formation as  to  the  nature  of  these  plants,  may  bo  stated  as  follows: 

Schimper,  in  his  '*  Paheontologie  Vegetale  "  (possibly  from  Inat- 
tention to  the  descriptions  or  want  of  access  to  specimens),  doubts  the 
lycopodiaceous  character  of  species  of  Lycopodites  described  in  my 
published  papers  on  plants  of  the  Devonian  of  America  and  in  my 
Report  of  1871.  Of  these,  L,  Richardnoni  and  L,  Mntthen'i  are  un- 
doul)tedly  very  near  to  the  modern  genus  Lyrnpodiutn.  L.  Vaniir- 
einii  is,  I  admit,  more  problematical ;  but  Schimper  could  scarcely 
have  supi)osed  it  to  be  a  fern  or  a  fucoid  allied  to  Caulerpa  had  he 
observed  that  both  in  my  species  and  the  allied  L.  peniupformla  of 
Goeppert,  which  he  does  not  appear  to  notice,  the  pinnules  are  ar- 
ticulated upon  the  stem,  and  leave  scars  where  they  have  fallen  oil. 
When  in  Belfast  in  1870,  my  attention  was  again  directed  to  the 
af\  lities  of  these  plants  by  finding  in  Prof.  Thomson's  collection  a 
sp-oim'^n  from  Caithness,  which  shows  a  plant  apparently  of  this 
kind,  v.ith  the  same  long  narrow  pinna;  or  leaflets,  attached,  how- 
ever, to  thicker  stems,  and  rolled  up  in  a  circinate  manner.  It  seems 
to  be  a  plant  in  vernation,  and  the  parts  are  too  much  c.owded  and 
pressed  together  to  admit  of  being  accurately  figured  or  described  ; 
but  1  think  I  can  scarcely  be  deceived  as  to  its  true  nature.  The 
circinate  arrangement  in  this  case  would  favour  a  relationship  to 
ferns ;  but  some  lycopodiaceous  plants  also  roll  themselves  in  this 
way,  and  so  do  the  branches  of  the  plants  of  the  genus  Psilophyton. 
(Fig.  17,  supra.) 

The  specimen  consists  of  a  short,  erect  stem,  on  which  are  placed 
somewhat  ^tout  alternate  branches,  extending  obliquely  outward  and 
then  curving  inward  in  a  circinate  manner.  The  lower  onos  appear 
to  produce  on  their  inner  sides  short  lateral  branchlets,  and  upon 
these,  and  also  upon  the  curved  extremities  of  the  branches,  are  long, 
narrow,  linear  leaves  place'  '"n  a  crowded  manner.  The  specimen  is 
thus  not  a  spike  of  fructi..  —..ion,  but  a  young  stem  or  branch  in  ver- 
nation, and  which  when  unrolled  would  be  of  the  form   of   those 


*  "Canadian  Naturalist,"  1878. 


88 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


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peculiar  pinnate  Lycopodites  of  which  L.  Vanuxemii  of  the  Ameri- 
can Devonian  and  L.  pennrpformis  of  the  European  Lower  Carbon- 
iferous are  the  types,  and  it  shows,  what  might  have  been  anticipated 
from  other  specimens,  that  they  were  low,  tufted  plants,  circinate  in 
vernation.  The  short  stem  of  this  plant  is  simply  furrowed,  and 
bears  no  resemblance  to  a  detached  branch  of  Lycopodites  Milleri 
which  lies  at  right  angles  to  it  on  the  same  slab.  As  to  the  affinities 
of  the  singular  type  of  plants  to  which  this  specimen  belongs,  I  may 
quote  from  my  "  Ileport  on  the  Lower  Carboniferous  Plants  of 
Canada."  in  which  I  have  described  an  allied  species,  L.  plumula : 

"  The  botanical  relations  of  these  plants  must  remain  subject  to 
doubt,  until  either  their  internal  structure  or  their  fructification  can 
be  discovered.  In  the  mean  time  I  follow  Goeppert  in  placing  them 
in  what  we  must  regard  as  the  provisional  genus  Lycopodites.  On 
the  one  hand,  they  are  not  unlike  the  slender  twigs  of  Taxodium 
and  similar  Conifers,  and  the  highly  carbonaceous  character  of  the 
stems  gives  some  colour  to  the  supposition  that  they  may  have  been 
woody  plants.  On  the  other  hand,  they  might,  so  far  as  form  is  con- 
cerned, be  placed  with  Alga^  of  the  type  of  Brongniart's  Chondrites 
ohtusi's,  or  the  modern  Caulerpa  j)lumaria.  Again,  in  a  plant  of 
this  type  from  the  Devonian  of  Caithness  to  which  I  have  referred  in 
a  former  memoir,  the  vernation  seems  to  have  been  circinate,  and 
Schimper  has  conjectured  that  these  plants  may  be  ferns,  which 
seems  also  to  have  been  the  view  of  Shumard." 

On  the  whole,  these  plants  are  allied  to  Lycopods  rather  than  to 
ferns ;  and  as  they  constitute  a  small  but  distinct  group,  known  only, 
so  far  as  I  am  aware,  in  the  Lower  Carboniferous  and  Erian  or  De- 
vonian, they  deserve  a  generic  name,  and  I  proposed  for  them  in  my 
"  Paper  on  Scottish  Devonian  Plants,"  1878,  that  of  Ptilophyton,  a 
name  sufficiently  distinct  in  sound  from  Psilophyton,  and  expressing 
very  well  their  peculiar  feather-like  habit  of  growth.  The  genus  was 
doflned  as  follows : 

"  Branching  plants,  the  branches  tearing  long,  slender  leaves  in 
two  or  more  ranks,  giving  them  a  feathered  appearance ;  vernation 
circinate.  Fruit  unknown,  but  analogy  would  ind.cato  that  it  was 
borne  on  the  bases  of  the  leaves  or  on  modified  branches  with  shorter 
leaves." 

The  Scottish  specimen  above  referred  to  was  named  Pt.  Thom- 
8oni,  and  was  characterised  by  its  densely  tufted  form  and  thick 
branches.  The  other  species  known  are:  Pi.  penna'forinis,  Goep- 
pert, L.  Carboniferous ;  Pt.  Vanuxemii,  Dawson,  Devonian ;  Pt, 
plumula,  Dawson,  L.  Carboniferous. 


TUE  BRIAN   OR  DEVONIAN  FORESTS. 


89 


Shnmar(Vs  Filicites  gracilis,  from  the  Lavonian  of  Ohio,  and 
Stur's  Pinites  antecedens,  from  the  Lower  Carboniferous  of  Silesia, 
may  possibly  belong  to  the  same  genus.  The  Scottish  specimen  re- 
ferred to  is  apparently  the  first  nppcarance  of  this  form  in  the 
Devonian  of  p]urope. 

I  have  at  a  still  later  date  had  opportunities  of  studying  con- 
siderable series  of  these  plants  collected  by  Prof.  Williams,  of  Cornell 
University,  and  prepared  a  note  in  reference  to  them  for  the  Ameri- 
can Association,  of  which,  however,  only  an  abstract  has  been  pub- 
lished. I  have  also  been  favoured  by  Prof.  Losquereux  and  Mr. 
Lacoe,  of  Pitt3ton,  with  the  opportunity  of-  studying  the  specimens 
referred  to  Trochophi/llum. 

Prof.  Williams's  specimens  occur  in  a  dark  shale  associated  with 
remains  of  land-plants  of  the  genera  Psilophyton,  Rhodea,  &c..  and 
also  marine  shells,  of  which  a  small  species  of  RhynchoneUa  is  often 
attached  to  the  stems  of  the  Ptilophylon.  Thus  these  organisms 
have  evidently  been  deposited  in  marine  beds,  but  in  association 
witii  land-plants. 

The  study  of  the  specimens  collected  by  Prof.  Williams  develops 
the  following  facts:  (1)  Tlie  plants  are  not  continuous  fronds,  but 
slender  stems  or  petioles,  with  narrow,  linear  leaflets  attached  in  a 
pinnate  manner.  (2)  The  pinnules  are  so  articulated  that  they  break 
off,  leaving  delicate  transverse  scars,  and  the  lower  parts  of  the  stems 
are  often  thus  denuded  of  pinna>  for  the  length  of  one  or  more 
inches.  (3)  Tlie  stems  curve  in  such  a  manner  as  to  indicate  a  cir- 
cinate  vernation.  (4)  In  a  few  instances  the  fronds  were  observed 
to  divide  dichotomously  toward  the  top ;  but  this  is  rare.  (5)  There 
are  no  indications  of  cells  in  the  pinnules;  but,  on  the  other  hand, 
there  is  no  appearance  of  fructification  unless  the  minute  granules 
which  roughen  some  of  the  stems  are  of  this  nature.  ((!)  The  stems 
seem  to  have  been  lax  and  flexuous,  and  in  some  instances  they 
seem  to  have  grown  on  the  petioles  of  ferns  preserved  with  them  in 
the  same  beds.  (7)  The  frequency  of  the  attachment  of  small  braehio- 
pods  to  the  specimens  of  Ptiloplujton  would  seem  to  indicate  that 
the  plant  stood  erect  in  the  water.  (8)  Some  of  the  specimens  show 
so  much  carbonaceoiis  matter  as  to  indicate  that  the  pinnules  were 
of  considerable  consistency.  All  these  characters  are  those  rather 
of  an  aquatic  plant  than  of  an  annual  organism  or  of  a  land-plant. 

The  specimens  communicated  by  Prof.  Lestiuoreux  and  Mr. 
Lacoe  are  from  the  Lower  Carboniferous,  and  evidently  represent  a 
different  specie  with  similar  slender  pitted  stems,  often  partially 
denuded  of  pinnules  below ;  but  the  pinnules  are  much  broader  and 


I 


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THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


more  distant.  They  are  attached  by  very  narrow  bases,  and  ap- 
parently tend  to  lie  on  a  plane,  though  they  may  possibly  have  been 
spirally  arranged.  On  the  same  slabs  are  rounded  sporangia  or 
maerospores  like  those  of  Lepidodendron,  but  there  is  no  evidence 
that  these  belonged  to  Trochophyllvm.  On  the  stems  of  this  plant, 
however,  there  are  small,  rounded  bodies  apparently  taking  the  places 
of  some  of  the  pinnules.  These  may  possibly  be  spore-cases ;  but 
they  may  be  merely  imperfectly  developed  pinnules.  Still  the  fact 
that  similar  small  granules  appear  on  the  stems  of  the  Devonian 
species,  favours  the  idea  that  they  may  be  organs  of  fructification. 

The  most  interesting  discovery,  however,  which  results  from  the 
study  of  Mr.  Lacoe's  specimens,  is  that  the  pinnules  were  cylindrical 
and  hollow,  and  probably  served  to  iioat  the  plant.  This  would 
account  for  many  of  the  peculiarities  in  the  appearance  and  mode 
of  occurrence  of  the  Devonian  Ptilophyton,  which  arc  readily  ex- 
plained if  it  is  supposed  to  be  an  aquatic  plant,  attaching  itself  to 
the  stems  of  submerged  vegetable  remains  and  standing  erect  in  the 
water  by  virtue  of  its  hollow  leaves.  It  may  well,  however,  have 
been  a  plant  of  higher  organisation  than  the  AlgiT,  though  no  doubt 
cryptogamous. 

The  species  of  Ptilophyton  will  thus  constitute  a  peculiar  group 
of  aquatic  plants,  belonging  to  the  Devonian  and  Lower  Carbonif- 
erous periods,  and  perhaps  allied  to  Lycopods  and  Pillworts  in  their 
organisation  and  fruit,  but  specially  distinguished  by  their  linear 
leaves  serving  as  floats  and  arranged  pinnately  on  slender  stems. 
The  only  species  yet  found  within  the  limits  of  Canada  is  Pt.  phi- 
mula,  found  by  Dr.  Iloneyman  in  the  Lower  Carboniferous  of  Nova 
Scotia ;  but  as  Pt.  Vanuxemii  abounds  in  the  Erian  of  New  York, 
it  will  no  doubt  be  found  in  Canada  also. 

III. — Tree-Ferns  of  the  Erian  Period. 

As  the  fact  of  the  occurrence  of  true  tree-ferns  in  rocks  so  old 
as  the  Middle  Erian  or  Devonian  has  been  doubted  in  some  quar- 
ters, the  following  summary  is  given  from  descriptions  published  in 
the  "Journal  of  the  Geological  Society  of  Loudon"  (1871  and  1881), 
where  figures  of  the  species  will  be  found : 

Of  the  numerous  ferns  now  known  in  the  Middle  and  Upper 
Devonian  of  North  America,  a  great  number  are  small  and  delicate 
species,  which  were  {)robably  herbaceous ;  but  there  are  other  species 
which  may  have  been  tree-ferns.  Little  definite  information,  how- 
ever, has,  until  recently,  been  obtained  with  regard  to  their  habit  of 
growth. 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


91 


The  only  species  known  tc  ne  in  the  Devonian  of  Europe  is  the 
Canlopteris  Peachii  of  Salter,  figured  in  the  '•  Quarterly  Journal  of 
the  Geological  Society  "  for  1858.  The  original  specimen  of  this  I 
had  an  opportunity  of  seeing  in  London,  through  the  kindness  of 
Mr.  Etheridge,  and  have  no  doubt  that  it  is  the  stem  of  a  small 
arborescent  fern,  allied  to  the  genus  Caiilopteris,  of  the  coal  forma- 
tion. 

In  my  paper  on  the  Devonian  of  Eastern  America  ("  Quarterly 
Journal  of  the  Geological  Society,"  1802),  I  mentioned  a  plant  found 
by  Mr.  Richardson  at  Perry,  as  possibly  a  species  of  Metjophyton, 
using  that  term  to  denote  those  stems  of  tree-ferns  which  have  the 
leaf-scars  in  two  vertical  series ;  but  the  specimen  was  obscure,  and 
I  have  not  yet  obtained  any  other. 

Moie  recently,  in  1869,  Prof.  Hall  placed  in  my  hands  an  inter- 
esting collection  from  Gilboa,  New  York,  and  Madison  County,  New 
York,  including  two  trunks  surrounded  by  aerial  roots,  which  I  have 
described  as  Psaronius  fexiilis  and  P.  Erianus,  in  my  "  Revision  of 
the  Devonian  Flora,"  read  before  the  Royal  Society.*  In  the  same 
collection  were  two  very  large  petioles,  Rhachiopteria  gigantea  and 
li.  palmata,  which  I  have  suggested  may  have  belonged  to  tree-ferns. 

My  determination  of  the  species  of  Psaronius,  above  mentioned, 
has  recently  been  completely  confirmed  by  the  discovery  on  the  part 
of  Mr.  Lockwood,  of  Gilboa,  of  the  upper  part  of  one  of  these  stems, 
with  its  leaf-scars  preserved  and  petioles  attached,  and  also  by  some 
remarkable  specimens  obtained  by  Prof.  Newberry,  of  New  York, 
from  the  Corniferous  limestone  of  Ohio,  which  indicate  the  exist- 
ence there  of  three  species  of  tree-ferns,  one  of  them  with  aerial 
roots  similar  to  those  of  the  Gilboa  specimens.  The  whole  of  these 
specimens  Dr.  Newberry  has  kindly  allowed  me  to  examine,  and  has 
permitted  me  to  describe  the  Gilboa  specimen,  as  connected  with 
those  which  I  formerly  studied  in  Prof,  flail's  collections.  The 
specimens  from  Ohio  he  has  himself  named,  but  allows  me  to  notice 
them  here  by  way  of  comparison  with  the  others.  I  shall  add  some 
notes  on  specimens  found  with  the  Gilboa  ferns. 

It  may  be  further  observed  that  tlie  Gilboa  specimens  are  from 
a  bed  containing  erect  stumps  of  tree-ferns,  in  the  Chemung  group 
of  the  Upper  Devonian,  while  .hose  from  Oliio  are  from  a  marine 
limestone,  belonging  to  the  lower  part  of  the  Middle  Devonian. 

1.  Caulopteris  Lockwoodi,  Dawson. — Trunk  from  two  to  three 


*  Abstract  in  "  Proceedinps  of  the  Royal  Society,"  May,  1810;  also 
"Report  on  Brian  Plants  of  Canada,"  \671. 


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92 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


inches  in  diameter,  rugose  longitudinally.  Leaf-scars  broad,  rounded 
above,  and  radiatingly  rugose,  with  an  irregular  scar  below,  arranged 
spirally  in  about  five  ranks;  vascular  bundles  not  distinctly  pre- 
served. Petioles  slender,  much  expanded  at  the  base,  dividing  at 
first  in  p.  piimate  manner,  and  afterwards  dichotomously.  Ultimate 
pinnae  with  remains  of  numerous,  apparently  narrow  pinnules. 

This  stem  is  probably  the  upper  part  of  one  or  oth  r  of  the 
species  of  Psaronius  found  in  the  sanie  bed  (P.  Erianus,  Dawson, 
and  P.  fextilis,  Dawson).*  It  appears  to  have  been  an  erect  stem 
embedded  in  situ  in  sandstone,  and  preserved  as  a  cast.  The  stem 
is  small,  being  only  two  inches,  or  a  little  more,  in  diameter.  It 
is  coarsely  wrinkled  longitudinally,  and  covered  with  large  leaf- 
scars,  each  an  inch  in  diameter,  of  a  horseshoe-shape.  The  peti- 
oles, five  of  which  remain,  separate  from  these  scars  with  a  distinct 
articulation,  except  at  one  point  near  the  base,  where  probably  a 
bundle  or  bundles  of  vessels  passed  into  the  petiole.  They  retain 
their  form  at  the  attachment  to  the  stem,  but  a  little  distance 
from  it  they  are  flattened.  They  are  inflated  at  the  base,  and  some- 
what rapidly  diminish  in  size.  The  leaf-scars  vary  in  form,  and  are 
not  very  distinct,  but  they  appear  to  present  a  semicircular  row  of 
pits  above,  largest  in  the  middle.  From  these  there  proceed  down- 
ward a  series  of  irregular  furrows,  converging  to  a  second  and  more 
obscure  semicircle  of  pits,  within  or  below  which  is  the  irregular  scar 
or  break  above  referred  to.  The  attitude  and  form  of  the  petioles 
will  be  seen  from  Fig.  24,  supra. 

The  petioles  are  broken  off  within  a  few  inches  of  the  stem ; 
but  other  fragments  found  in  the  same  beds  appear  to  show  their 
continuation,  and  some  remains  of  their  foliage.  One  specimen 
shows  a  series  of  processes  at  the  sides,  which  seem  to  be  the  re- 
mains of  small  pinna),  or  possibly  of  spines  on  the  margin  of  the 
petiole.  Other  fragments  show  the  division  of  the  frond,  at  first  in 
u  pinnate  manner,  and  subsequently  by  bifurcation ;  and  some  frag- 
ments show  remains  of  pinnules,  possibly  of  fertile  pinnules.  These 
are  very  indistinct,  but  would  seem  to  show  that  the  plant  ap- 
proached, in  the  form  of  its  fronds  and  the  arrangement  of  its 
fructification,  to  the  Cyclopterids  of  the  subgenus  Aneimites,  one  of 
which  (Atieimites  Acadica),  from  the  Lower  Carboniferous  of  Nova 
Scotia,  I  have  elsewhere  described  as  probably  a  tree-fern.f     The 

*  Memoir  on  Devonian  Flora,  "  Proceedings  of  the  Royal  Society," 
May,  1870. 

t  "Quarterly  Journal  of  the  Geological  Society,"  1860.  .    - 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


93 


fronds  were  evidently  different  from  those  of  Archrpopteris,*  a  genus 
characteristic  of  tlie  same  beds,  but  of  very  different  habit  of  growth. 
This  accords  with  the  fact  tliat  there  is  in  Prof.  Hall's  collection  a 
mass  of  fronds  of  Cydopteris  (Archceopteris)  Jarksoni,  so  arranged 
as  to  make  it  probable  that  the  plant  was  an  herbaceous  fern,  pro- 
ducing tufts  of  fronds  on  short  stems  in  the  ordinary  way.  The 
obscurity  of  the  leaf-scars  may  render  it  doubtful  whether  the  plant 
above  described  should  be  placed  in  the  genus  Caulopferis  or  in  Stem- 
matopteris ;  but  it  appears  most  nearly  allied  to  the  former.  The 
genus  is  at  present,  of  course,  a  provisional  one;  but  I  have  thought 
it  only  justice  to  the  diligent  labours  of  Mr.  Lockwood  to  name 
this  curious  and  interesting  fossil  Caulopferis  Lockwoodi, 

I  have  elsewhere  remarked  on  the  fact  that  trunks,  and  petioles, 
and  pinnules  of  ferns  are  curiously  dissociated  in  the  Devonian  beds 
— an  effect  of  water-sorting,  characteristic  of  a  period  in  which  the 
conditions  of  deposition  were  so  varied.  Another  example  of  this 
is,  that  in  the  sandstones  of  Gaspe  Bay,  which  have  not  as  yet  af- 
forded any  example  of  fronds  of  ferns,  there  are  compressed  trunks, 
which  Mr.  Lockwood's  specimens  allow  me  at  least  to  conjecture 
may  have  belonged  to  tree-ferns,  although  none  of  them  are  suffi- 
ciently perfect  for  description. 

Mr.  Lockwood's  collection  includes  specimens  of  Psaronius  fex- 
tilis  ;  and  in  addition  to  these  there  are  remains  of  erect  stems  some- 
what different  in  character,  yet  possibly  belonging  to  the  higher  parts 
of  the  same  species  of  tree-fern.  One  of  these  is  a  stem  crushed  in 
such  a  manner  that  it  does  not  exhibit  its  form  with  any  distinctness, 
but  surrounded  by  smooth,  cylindrical  roots,  radiating-  from  it  in 
bundles,  proceeding  at  first  horizontally,  and  then  curving  down- 
ward, and  sometimes  terminating  in  rounded  ends.  They  resemble 
in  form  and  size  the  aerial  roots  of  Psaronius  Eriarms  ;  and  I  believe 
them  to  be  similar  roots  from  a  higher  part  of  the  stem,  and  some 
of  '^  \em  young  and  not  prolonged  sufficiently  far  to  reach  the  ground. 
This  specimen  would  thus  represent  the  stem  of  P.  Erianus  at  a 
higher  level  than  those  previously  found.  We  can  thus  in  imagirui- 
tion  restore  the  trunk  and  crown  of  this  once  graceful  tree-fern, 
though  we  have  not  the  detail  of  its  fronds.  Mr,  Lockwood's 
collections  also  contain  a  specimen  of  the  large  fern-petiole  which 
I  have  named  Rhachiopteris  punctata.  My  original  specimen 
was  obtained  by  Prof.  Hall  from  the  same  horizon  in  New  York. 


*  The  genus  to  which  the  well-known  Cyclopteris  {Adianiites)  Hiber- 
nieus  of  the  Devonian  of  Ireland  belongs. 

n 


t  i 


91 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


W 


That  of  Mr.  Lot  kwood  is  of  larger  size,  but  retains  no  remains  of  the 
frond.  It  must  have  belont^od  to  a  si)0('ics  quite  distinct  from  faw- 
lopteria  Loclcwoodi,  but  which  may,  like  it,  have  been  a  tree-fern. 

2.  Caulopte'iis  anticjua,  Newberry. — This  is  a  flattened  stem,  on 
a  slab  of  limestone,  containing  liiachiopods,  Trilobites,  &c.,  of  the 
Corniferous  limestone.  It  is  about  eighteen  inches  in  length,  and 
three  and  a  half  inches  in  average  breadth.  The  exposed  side  shows 
about  twenty-two  large  leaf -scars  arranged  spirally.  Each  leaf, 
where  broken  off,  has  left  a  rough  fracture ;  and  above  this  is  a 
semicircular  impression  of  the  petiole  against  the  stem,  which,  as 
well  as  the  surface  of  the  bases  of  the  petioles,  is  longitudinally 
striated  or  tuberculated.  The  structures  are  not  preserved,  but 
merely  the  outer  epidermis,  as  a  coaly  film.  The  stem  altogether 
much  resembles  Caulopteris  Peachii,  but  is  of  larger  size.  It  differs 
from  C.  Lockwoodi  in  the  more  elongated  leaf-bases,  and  in  the 
leaves  being  more  remotely  placed;  but  it  is  evidently  of  the  same 
general  character  with  that  species. 

3.  Caulopteris  (Protopteris)  peregrina,  Newberry.  —  This  is  a 
much  more  interesting  species  than  the  last,  as  belonging  to  a  ge- 
neric or  subgeneric  form  not  hitherto  recognised  below  the  Carbonif- 
erous, and  having  its  minute  structure  in  part  preserved. 

The  specimens  are,  like  the  last,  on  slabs  ot  marine  limestone  of 
the  Corniferous  formation,  and  flattened.  One  represents  an  uj)per 
portion  of  the  stem  with  leaf-scars  and  remains  of  petioles ;  another 
a  lower  portion,  with  aerial  roots.  The  upper  part  is  three  inches 
in  diameter,  and  about  a  foot  in  length,  and  shows  thirty  leaf-scars, 
which  are  about  three-fourths  of  an  inch  wide,  and  rather  less  in 
depth.  The  upper  part  presents  a  distinct  r'>unded  and  sometimes 
double  marginal  line,  sometimes  with  a  slight  depression  in  the  mid- 
dle. The  lower  part  is  irregular,  and  when  most  perfect  shows  seven 
slender  va«<^nlar  bundles,  passing  obliquely  downward  into  the  stem. 
The  more  [.  3t  leaf-bases  have  the  structure  preserved,  and  show 
a  delicate,  thin-walled,  oval  parenchyma,  while  the  vascular  bundles 
show  scalariform  vessels  with  short  bars  in  several  rows,  in  the  man- 
ner of  many  jnodern  ferns.  Some  of  the  scars  show  traces  of  the 
hippocrepian  mark  characteristic  of  I^otnpferis ;  and  the  arrange- 
ment of  the  vascular  bundles  at  the  base  of  the  scars  is  the  same  as 
in  that  genus,  as  are  also  the  general  form  and  arrangement  of  the 
scars.  (  1  careful  examination,  the  species  is  indeed  very  near  to  the 
typical  P.  Stembergii,  as  figured  by  Corda  and  Schimper.* 


*  Corda,  "  Beitrago,"  PI.  48,  copied  by  Schimper,  PI.  52. 


THE  ERIAN  OR  DEVONIAN   FORESTS. 


95 


The  genus  Protopfrris  of  Stornborg,  tliough  the  original  species 
(P.  punctata)  appears  as  a  Lepidodcndion  in  his  earlier  plate  (Plate 
4),  and  as  a  Siyilldria  {S.  jxuffafu)  in  Brongniart's  great  work,  is  a 
true  tree-fern;  and  the  structure  of  one  sjuHMes  (P.  Cottai)  has  been 
beautifully  figuered  by  Corda.  The  species  hitherto  descril)ed  are 
from  the  Carboniferous  and  Permian. 

The  second  specimen  of  this  species  represents  a  lower  part  of 
the  stem.  It  is  thirteen  inches  long  and  about  four  inches  in  diam- 
eter, and  is  covered  with  a  mass  of  flattened  aerial  rov>ts  lying  paral- 
lel to  each  other,  in  the  manner  of  the  Psaromtes  of  the  coal-forma- 
tion and  of  P.  J'Jrianus  of  the  Upper  Erian  or  Devonian. 

4.  Asteropteris  novehoracensis,  gen.  and  sp.  n. — The  geniis  An- 
teropteris  is  established  for  stems  of  ferns  having  the  axial  portion 
composed  of  vertical  radiating  plates  of  scalariform  tissue  embedded 
in  parenchyma,  and  having  the  outer  cylinder  composed  of  elongated 
cells  travei*sed  by  leaf-bundles  of  the  type  of  those  of  Zijgnpteris. 

The  only  species  known  to  me  is  represented  by  a  stem  2*5  cen- 
timetres in  diameter,  slightly  wrinkled  and  pitted  externally,  per- 
haps by  traces  of  aerial  roots  which  have  perished.  The  transverse 
section  shows  in  the  centre  four  vertical  plates  of  scalariform  or  im- 
perfectly reticulated  tissue,  placed  at  right  angles  to  each  other,  and 
united  in  the  middle  of  the  stem.  At  a  short  distance  from  the 
centre,  each  of  these  plates  divides  into  two  or  three,  so  as  to  form 
an  axis  of  from  ten  to  twelve  radiating  plates,  with  remains  of  cellu- 
lar tissue  filling  the  angidar  interspaces.  The  greatest  diameter  of 
this  axis  is  about  1*5  centimetre.  p]xterior  to  the  axis  the  stem  con- 
sists of  elongated  colls,  with  somewhat  thick  walls,  and  more  dense 
toward  the  circumference.  The  walls  of  these  cells  present  a  curious 
reticulated  appearance,  apparently  caused  by  the  cracking  of  the 
ligneous  lining  in  consequence  of  contraction  in  the  process  of  car- 
bonization. Embedded  in  this  outer  cylinder  are  about  twelve  vas- 
cular bundles,  each  with  a  dumb-bell-shaped  group  of  scalariform 
vessels  enclosed  in  a  sheath  of  thick-walled  fibres.  Each  bundle  is 
opposite  to  one  of  the  rays  of  the  central  axis.  The  specimen  shows 
about  two  inches  of  the  length  of  the  stem,  and  is  somewhat  bent, 
aj)parently  by  pressure,  at  one  end. 

This  stem  is  evidently  that  of  a  small  tree-fern  of  a  type,  so 
far  as  known  to  me,  not  before  described,*  and  constituting  a  very 
complex  and  symmetrical  form  of  the  group  of  PaliBozoic  ferns  allied 


*  Prof,  Williamson,  to  whom  I  have  sent  a  tracing  of  the  structure, 


agrees  with  mc  that  it  is  new. 


(1 


90 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


ii 


m 


j  ■ 

-■ 

7 

1  ' 

• 

t 

m 

m. 

to  the  penus  Zyffopteris  of  Sohimper.  The  central  axis  alone  has  a 
curious  resembhince  to  the  peculiar  stem  described  by  linger  ("De- 
vonian Flora  of  Thuringia ")  under  the  name  of  Cladoxylon  mira- 
hile ;  and  it  is  just  possible  that  this  latter  stem  may  be  the  axis 
of  sonic  allied  plant.  The  large  aerial  roots  of  some  modern  tree- 
ferns  of  the  genus  Angiopteria  have,  however,  an  analogous  radiating 
structure. 

The  specimen  is  from  the  collection  of  Berlin  IT.  Wright,  Esq., 
of  Penn  Yan,  New  York,  and  was  found  in  the  Portage  group  (Upper 
Erian)  of  Milo,  New  York,  where  it  was  associated  with  large  petioles 
of  ferns  and  trunks  of  Lepidodendra,  probably  L.  Chemungetise  and 
L.  prinuevum. 

The  occurrence  of  this  and  other  stems  of  tree-ferns  in  marine 
beds  has  recently  been  illustrated  by  the  observation  of  Prof.  A. 
Agassiz  that  considerable  quantities  of  vegetable  mutter  can  be 
dredged  from  great  depths  in  the  sea  on  the  leeward  side  of  the 
Caribbean  Islands.  The  occurrence  of  these  trunks  further  connects 
itself  with  the  great  abundance  of  large  petioles  {Rhachiopteris)  in 
the  same  beds,  while  the  rarity  of  well-preserved  fronds  is  explained 
by  the  coarseness  of  the  beds,  and  also  by  the  probably  long  macera- 
tion of  the  plant-remains  in  the  sea-water. 

In  connection  with  this  I  may  refer  to  the  remarkable  facts  re- 
cently stated  by  Williamson*  respecting  the  stems  known  as  Hete- 
rangium  and  Lyginodendron.  It  would  seem  that  these,  while  having 
strong  exogenous  peculiarities,  are  really  stems  of  tree-ferns,  thus 
placing  this  family  in  the  same  position  of  advancement  with  the 
Lycopods  and  Equisetacece  of  the  Coal  period. 

•    IV. — On  Erian  Trees  of  the  Genus  Dadoxylon,  Under. 
{Araucarites  of  Goeppert,  Araucarioxylon  of  Kraus.) 

Large  woody  trunks,  carbonised  or  silicificd,  and  showing  wood- 
cells  with  hexagonal  areoles  having  oval  pores  inscribed  in  them, 
occur  abundantly  in  some  beds  of  the  Middle  Erian  of  America,  and 
constitute  the  most  common  kind  of  fossil  wood  all  the  way  to  the 
Trias.  They  have  in  the  older  formations,  generally,  several  rows 
of  pores  on  each  fibre,  and  medullary  rays  composed  of  two  or  more 
series  of  cells,  but  become  more  simple  in  these  respects  in  the  Per- 
mian and  Triassic  series.  The  names  Araucarites  and  Araucarioxy- 
lon  are  perhaps  objectionable,  inasmuch  as  they  suppose  affinities  to 
Araucaria  which  may  not  exist.      Unger's  name,  which  is  non- 

*  "Proceedings  of  the  Royal  Society,"  January  6,  1887. 


THE   BRIAN   OR   DEVONIAN  FORESTS. 


97 


committal,  is  tho.-eforo.  T  ihink,  to  be  preferrcfl.  In  my  "Acadian 
Geolojjy,"  and  in  my  "Kiporr  on  the  GeoIoj?y  of  Prince  Edward 
Island,''  I  have  given  reasons  for  hclievinj?  tliat  the  foliage  of  some 
at  least  of  these  trees  was  that  known  w.  Walrhm,  and  that  they  may 
have  borne  nutlets  in  the  manner  of  Taxiue  trees  (7V/(70Hocnr/>»/m, 
&c.).  Grand  d'Eury  has  recently  suggested  that  some  of  them  may 
liave  belonged  to  Cordnites,  or  to  plants  included  in  that  somewhat 
varied  and  probably  artificial  group. 

The  earliest  discovery  of  trees  of  this  kind  in  the  Erian  of 
America  was  that  of  Matthew  and  Ilartt,  who  found  large  trunks, 
which  I  afterwards  described  as  Dadoi-yUm  Ouangnnd ianum,  in  the 
Erian  sandstone  of  St.  John,  New  Brunswick,  hence  named  by  those 
geologists  the  " Dadoxylon  sandstone."  A  little  later,  similar  wood 
was  found  by  Prof.  Hall  and  Prof.  Newberry  in  the  Hamilton  group 
of  New  York  and  Ohio^  and  the  allied  wood  of  the  genus  Ormoinjlon 
was  obtained  by  Prof.  Hall  in  the  Portage  group  of  the  former 
State.  These  woods  proved  to  be  specifically  distinct  from  that  of 
St.  John,  and  wore  named  by  me  T).  Halli,  D.  Newberryi,  and  Or- 
moxylon  Eriaiuim.  The  three  species  of  Dadojryhm  agreed  in  hav- 
ing composite  medullary  rays,  and  would  thus  belong  to  the  group 
Palfpoxyfon  of  Brongniart.  In  the  case  of  Ormoxylon  this  character 
could  not  be  very  distinctly  ascertained,  but  the  medullary  rays 
appeared  to  be  simple. 

I  am  indebted  to  Prof.  J.  M.  Clarke,  of  Amherst  College,  Massa- 
chusetts, for  some  well-preserved  specimens  of  another  species  from 
the  Genesee  shale  of  Canandaigua,  New  York.  They  show  small 
stems  or  branches,  with  a  cellular  pith  surrounded  with  wood  of 
coniferous  type,  showing  two  to  three  rows  of  slit-formed,  bordered 
pores  in  hexagonal  borders.  The  medullary  sheath  consists  of 
pseudo-scalariform  and  reticulated  fibres ;  but  the  most  remarkable 
feature  of  this  wood  is  the  structure  of  the  medullary  rays,  which 
are  very  frequent,  but  short  and  simple,  sometimes  having  as  few 
as  four  cells  superimposed.  This  is  a  character  not  before  observed 
in  coniferous  trees  of  so  great  age,  and  allies  this  Middle  Erian 
form  with  some  Carboniferous  woods  which  have  been  supposed  to 
belong  to  Cordailes  or  Siyillaria.  In  any  case  this  structure  is  new, 
and  I  have  named  the  species  Dadoxylon  Clnrkiiy  after  its  discoverer. 
The  specimens  occur,  according  to  Prof.  Clarke,  in  a  calcareous  layer 
which  is  filled  with  the  minute  shells  of  Styliola  fissure.lla  of  Hall, 
believed  to  be  a  Pteropod  ;  and  containing  also  shells  of  Goniatites 
and  Gyroceras.  The  stems  found  are  only  a  few  inches  in  diameter, 
but  may  be  branches  of  larger  trees. 


ii! 


M 


14  \ 

i 

i 

r             ! 
1   - 

I 
1 

98 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


It  thus  appears  that  wc  already  know  flvo  species  of  Coniferous 
trees  of  the  goniis  Dadoxylon  in  the  IVIiddle  Erian  of  America,  an 
interesting  confirmation  of  the  facts  otherwise  known  as  to  the 
great  richness  and  variety  of  this  ancient  flora.  The  late  Prof, 
(ioeppert  informed  me  that  he  had  recognised  similar  wood  in  the 
Devonian  of  Germany,  and  there  can  be  no  doubt  that  the  fossil 
wood  discovered  by  Hugh  Miller  in  the  Old  Red  Sanilstone  of  Scot- 
land, and  described  by  Salter  and  McNab,  is  of  similar  character,  and 
probably  belongs  to  the  genus  Dadoxylon.  Thus  this  type  of  Conif- 
erous tree  seems  to  have  been  as  well  established  and  differentiated 
into  species  in  the  Middle  Devonian  as  in  the  succeeding  Carbonif- 
erous. 

I  may  here  refer  to  the  fact  that  the  lower  limit  of  the  trees  of 
this  group  coincides,  in  America,  with  the  upper  limit  of  those  prob- 
lematical trees  which  in  the  previous  chapter  I  have  named  Proto- 
gens  {Nematophyton,  Celluloxlyon,*  Nematuxylon  f ),  though  Apo- 
roxylon  of  linger  extends,  in  Thuringia,  up  to  the  Upper  Devonian 
(Cypridina  schists), 

V. — Scottish  Devonian  Plants  of  Huon  Miller  and  others. 
(Edinburgh  Geological  Society,  1877.) 

Previously  to  the  appearance  of  my  descriptions  of  Devonian 
plants  from  North  America,  Hugh  Miller  had  described  forms  from 
the  Devonian  of  Scotland,  similar  to  those  for  which  I  proposed  the 
generic  name  Pailophyton  ;  and  I  referred  to  these  in  this  connection 
in  my  earliest  description  of  that  genus.ij:  He  had  also  recognised 
whr.L  seemed  to  bo  plants  allied  to  Lycopods  and  Conifers.  Mr. 
Peach  and  Mr.  Duncan  had  made  additional  discoveries  of  this  kind, 
and  Sir  J.  Hooker  and  Mr.  Salter  had  described  some  of  these  re- 
mains. More  recently  Messrs.  Peach,  Carruthers,  and  McNab  have 
worked  in  this  field,  and  still  later*  Messrs.  Jack  and  Etheridge 
have  summed  up  the  facts  and  have  added  some  that  are  new. 

The  first  point  to  which  I  shall  refer,  and  which  will  lead  to  the 
other  matters  to  be  discussed,  is  the  relation  of  the  characteristic" 
Lepidodendron  of  the  Devonian  of  eastern  America,  L.  Gaspianum, 
to  L.  nothum  of  Unger  and  of  Salter.     At  the  time  when  I  described 
this  species  I  had  not  access  to  Scottish  specimens  of  Lepidodendron 


*  "Journal  of  the  Geological  Society,"  May,  1881. 
f  Ibid.,  vol.  six,  1863. 

X  "  Journal  of  the  Geological  Society,"  London,  1859. 
«  Jbid.,  1877. 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


09 


from  the  Devonian,  but  these  had  been  well  fipirod  nnd  described 
by  Salter,  imtl  had  boon  idontifiod  with  L,ni)thumoi  Unjjor,  a  species 
evidently  distinct  from  mine,  as  was  also  thai  fif:;ured  and  described 
by  Suiter,  whether  identical  or  not  with  Unger's  species.  In  1870 
I  had  for  the  first  time  an  opportunity  to  study  Scottish  specimens 
in  the  collection  of  Mr.  Peacii ;  anil  on  the  evidence  thus  alfordod  I 
stated  confidently  that  these  specimens  represented  a  species  distinct 
from  L.  Oaspianum,  perhaps  oven  generically  so.*  It  differs  from 
L,  Oaspianum  in  its  habit  of  growth  by  developing  small  lateral 
branches  instead  of  bifurcating,  and  in  its  foliage  by  the  absence  or 
obsolete  character  of  the  leaf-bases  and  the  closely  placed  and  some- 
what appressed  leaves.  If  an  ai)pearance  of  sw(  lling  at  the  end  of  a 
lateral  branch  in  one  specimen  indicates  a  strobile  of  fructification, 
then  its  fruit  was  not  dissimilar  from  that  of  the  Canadian  species 
in  its  position  and  general  form,  though  it  may  have  differed  in 
details.  On  these  grounds  I  declined  to  identify  the  Scottish  species 
with  L.  Gaspianum.  The  Lepidodondron  from  the  Devonian  of 
Belgium  described  and  figured  by  Crepin.f  has  a  better  claim  to  such 
identification,  and  would  seem  to  prove  that  this  species  existed  in 
Europe  as  well  as  in  America.  I  also  saw  in  Mr.  Peach's  collection 
in  1870  some  fragments  which  seemed  to  me  distinct  from  Salter's 
species,  and  possibly  belonging  to  L.  Gaspianum.X 

In  the  earliest  description  of  Pmlophyton  I  recognised  its  prob- 
able generic  alTinity  with  Miller's  "  dichotomous  plants,"  with  Salter's 
"  rootlets,"  and  with  Goeppert's  Haliserites  Dechenianns,  and  stated 
that  I  had  "  little  doubt  that  materials  exist  in  the  Old  Red  Sand- 
stone of  Scotland  for  the  reconstruction  of  at  least  one  species  of 
this  genus."  Since,  however.  Miller's  plants  had  been  referred  to 
coniferous  roots,  and  to  fueoids,  and  Goeppert's  Haliserites  was  a 
name  applicable  only  to  fueoids,  and  since  the  structure  and  fruit 
of  my  plants  placed  them  near  to  Lycopods,  I  was  under  the  neces- 
sity of  giving  them  a  special  generic  name,  nor  could  I  with  cer- 
tainty alfirm  their  specific  identity  with  any  Euroi)ean  species.  The 
comparison  of  the  Scottish  specimens  with  woody  rootlets,  though 
incorrect,  is  in  one  respect  creditable  to  the  acumen  of  Salter,  as  in 
almost  any  state  of  preservation  an  experienced  ej  e  can  readily  per- 
ceive that  branchlets  of  Psilophyton  must  have  'oeen  woody  rather 


*  "Report  on  Devonian  Plants  of  Canada,"  ISVl. 

f  "Observations  sur  quelques  Plantes  Fossiles  des  ddpots  Devoni- 


ens. 


X  "  Proceedings  of  the  Geological  Society  of  London,"  March,  1871. 


' ;  ^ 


I  s 
in    1, 


A 


1:| 


f  ft' 
I  I 


it 

19  f     I 


4 


100 


TUE  GEOLOGICAL   HISTORY  OF  PLANTS. 


than  horbnronus,  and  their  appearance  is  qxiito  different  from  that 
of  any  true  Alfitv. 

TIjo  type  of  I'silnpfii/fon  is  my  P.  princepn,  of  wliich  the  whole 
of  the  parts  and  structures  arc  well  i<iiown,  the  entire  plant  being 
furnished  in  abundance  and  in  m'tu  in  the  ridi  |»lant-beds  of  Gaspc. 
A  second  species,  J'.  rn/)Ufiliii.i,  has  also  afforded  well-characterised 
fructification.  P.  eleyanfi,  vfhosa  fruit  appears  as  "oval  scales,"  no 
doubt  bore  sac-like  spore-cases  resembling  those  of  the  other  species, 
but  in  a  dilTercnt  position,  and  perfectly  flattened  in  the  specimens 
procured.  The  only  other  Caruidiati  species,  /*.  glabrum,  being  some- 
what different  in  appearance  from  the  others,  and  not  having  af- 
forced  any  fructification,  must  be  regarded  as  uncertain. 

The  generic  characters  of  the  first  three  species  may  be  stated  as 
follows : 

Stems  dichotomous,  with  rudimentary  subulate  leaves,  sometimes 
obsolete  in  terminal  branchlets  and  fertile  branches ;  and  in  decor- 
ticated specimens  represented  only  by  punctiform  scars.  Young 
branches  circinate.  Rlnzomata  cylindrical,  with  circular  root- 
areoles.  Internal  structure  of  stem,  an  axis  of  scalariform  vessels 
enclosed  in  a  sheath  of  imperfect  woody  tissue  and  covered  with  a 
cellular  bark  more  dense  externally.  Fruit,  naked  sac-like  spore- 
cases,  in  pairs  or  clusters,  terminal  or  lateral. 

The  Scottish  specimens  conform  to  these  characters  in  so  far  as 
they  are  known,  but  not  having  as  yet  afforded  fniit  or  internal 
structure,  they  cannot  be  specifically  determined  with  certainty. 
More  complete  specimens  should  be  carefully  searched  for,  and  will 
no  doubt  be  found. 

In  Belgium,  M.  Crepin  has  described  a  new  species  from  the 
Upper  Devonian  of  Condroz  under  the  name  P.  Condrusianum 
(1875).  It  wants,  however,  some  of  the  more  important  characters  of 
the  genus,  and  differs  in  having  a  pinnate  ramification,  giving  it  ^\\q 
aspect  of  a  fern.  In  a  later  paper  (1876)  the  author  considers  tn.s 
species  distinct  from  Psilophyton,  and  proposes  for  it  a  new  generic 
name  Rhacophyton. 

The  characters  given  by  Mr.  Carruthers,  in  his  paper  of  1873,  for 
the  species  P.  Dechenianum,  are  very  few  and  general :  "  Lower 
branches  short  and  frequently  branching,  giving  the  plant  an  oblong 
circumscription."  Yet  even  these  characters  do  not  apply,  so  far  a? 
known,  to  Miller's  fucoids  or  Salter's  rootlets  or  Goeppert's  Ilalise- 
rites.  They  merely  express  the  peculiar  mode  of  branching  already 
referred  to  in  Salter's  Lepidodetidron  nothum.  The  identification  of 
the  former  plants  with  the  Lepidodendron  and  Lycopodif.es,  indeed, 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


101 


rpslsonly  on  more  juxtaposition  of  frngmonts,  and  on  the  Hlipht  rosoin- 
blanoo  of  the  dooorticntocl  ends  of  tho  hranchos  of  the  latter  plants 
to  pHihphi/fon,  It  is  contradicted  by  the  obtuse  ends  of  the 
branches  of  tho  Lepidndendron  and  Li/ropodifeti,  and  by  the  apj)ar- 
ently  strobilaceous  termination  of  some  of  them. 

Salter's  descrijit ion  of  \m  Lcpitlodendntn  uothnvi  is  quite  defi- 
nite, and  accords  with  specimens  placed  in  my  hands  by  Mr.  i'each : 
"Stems  Imlf  an  inch  broad,  taperinp:  little,  branchc  short :  set  on  at 
an  acute  angle,  blunt  at  their  teriniiuitions.  Loaves  in  seven  to  ten 
rows,  very  short,  not  a  line  long,  and  rather  spreading  than  closely 
imbricate."  These  charactei-s,  however,  in  so  far  as  they  go,  are 
rather  those  of  the  genus  Lycopodilen  than  of  Lcpidodvndron,  from 
which  this  plant  differs  in  wanting  any  distinct  leaf-bases,  and  in  its 
short,  crowded  leaves.  It  is  to  be  observed  that  they  ajiply  also  to 
Salter's  Lycopodifes  MiUeri,  and  that  the  (^'(Terence  of  the  foliage 
of  that  species  may  be  a  result  merely  of  dillerent  state  of  preser- 
vation. For  these  reasons  I  am  disposed  to  place  these  two  sup- 
posed species  together,  and  to  retain  for  the  species  tho  name 
Lycopodifes  Miller i.  It  may  be  characterised  by  the  descri{)tion 
above  given,  with  merely  the  modification  that  the  leaves  are  some- 
times nearly  one-third  of  an  inch  long  and  secund  (Fig.  17,  supra, 
lower  figure). 

Decorticated  branches  of  tho  above  species  may  no  douot  be  mis- 
taken for  Psilnphyton,  but  are  nevertheless  quite  distinct  from  it,  and 
the  slender  branching  dichotomous  stems,  with  terminations  wfiich, 
as  Miller  graphically  states,  are  "  like  the  tendrils  of  a  pea,"  are  too 
characteristic  to  bo  easily  mistaken,  even  when  neither  fruit  nor 
leaves  appear.  With  reference  to  fructification,  the  form  of  L. 
Milleri  renders  it  certain  that  it  must  have  borne  strobiles  at  the 
ends  of  its  branchlets,  or  some  substitute  for  these,  and  not  naked 
spore-cases  like  those  of  Psilophyton, 

The  remarkable  fragment  communicated  by  Sir  Philip  Egerton 
to  Mr.  Carruthers,*  belongs  to  a  third  grouj).  anil  has,  I  think,  been 
quite  misunderstood.  I  am  enabled  to  make  this  statement  with 
some  confidence,  from  tho  fact  that  the  reverse  or  counterpart  of  Sir 
Philip's  specimen  was  in  the  collection  of  Sir  Wyville  Thomson,  and 
was  placed  by  him  in  my  hands  in  1870.  It  was  noticed  in  my 
paper  on  "  New  Devonian  Plants,"  in  the  "  Journal  of  the  Geologi- 
cal Society  of  London,"  and  referred  to  my  genus  Itilopfiyton,  as 
stated  above  under  Section  II.,  page  8G  et  seq. 


*  "Journal  of  Botany,"  1873. 


I 


;ft 


102 


THE   GEOLOGICAL  UISTORY  OF  PLANTS. 


Mr.  Salter  doscribed,  in  1857,*  fragments  of  fossil  wood  from  the 
Scottish  Devonian,  having  the  structure  of  Dadoxylon,  though  very 
imperfectly  preserved ;  and  Prof.  McNab  has  proposed  f  the  generic 
name  Palaopitys  for  another  specimen  of  coniferous  wood  collected 
by  Hugh  Miller,  and  referred  to  by  him  in  the  "Testimony  of  the 
Rocks."  From  Prof,  McNab's  description,  I  should  infer  that  this 
wood  may,  after  all,  be  generically  identical  with  the  woods  usually 
referred  to  Dadoxylon  of  Unger  {Araur.arioxylon  of  Kraus).  The 
description,  however,  does  not  mention  the  number  and  disposition 
of  the  rows  of  pores,  nor  the  structure  of  the  medullary  rays,  and  I 
have  not  been  able  to  obtain  access  to  the  specimens  themselves.  1 
have  described  five  species  of  Dadoxylon  from  the  Middle  and  Up- 
per Erian  of  America,  all  quite  distinct  from  the  Lower  Carbonifer- 
ous species.  There  is  also  one  species  of  an  allied  genus,  Ormoxylon. 
All  these  have  been  carefully  figured,  and  it  is  much  to  be  desired 
that  the  Scottish  specimens  should  be  re-examined  and  compared 
with  them. 

Messrs.  Jack  and  Etheridgo  have  given  an  excelleni  summaiy 
of  our  present  knowledge  of  the  Devonian  flora  of  Scotland,  in  the 
Journal  of  the  London  Geological  Society  (1877).  From  this  it 
would  appear  that  species  referable  to  the  genera  Calamites,  Lepi- 
dodendron,  Lycopodites,  PHilophyton,  Arthrostigma,  ArcJueopteris, 
Caulop/eris,  Palmopitys,  Araucarioxylon,  and  Stiginaria  have  been 
recognised. 

The  plants  described  by  these  gentlemen  from  the  Old  Red 
Sandstone  of  Cal lender,  I  should  suppose,  from  their  figures  and 
descriptions,  to  belong  to  the  gnus  Arthrostigma,  rather  than  to 
Psilophyton.  I  do  not  attach  any  importance  to  the  suggestions  re- 
ferred to  by  them,  that  the  apparent  leaves  may  be  leaf-bases.  Long 
leaf-bases,  like  those  characteristic  of  Lepidofloyos,  do  not  occur  in 
these  humbler  plants  of  tiic  Devonian.  The  stems  with  delicate 
"  horizontal  processes  "  to  w  hich  they  refer  may  belong  to  Plilophy- 
ton  or  to  Pinnularia. 

In  conclusion,  I  need  scarcely  say  that  I  do  not  share  in  the 
doubts  expressed  by  some  British  pahrontologists  as  to  the  distinct- 
ness of  the  Devonian  and  Carboniferous  floras.  In  eastern  America, 
where  these  formations  are  mutually  unconformable,  there  is,  of 
course,  less  room  for  doubt  than  in  Ireland  and  in  western  Ameri- 
ca, where  they  are  stratigraphically  continuous.    Still,  in  passing 

*  "  Journal  of  the  London  Geological  Society." 

f  "Transactions  of  the  Edinburgh  Botanical  Society,"  1870. 


THE  BRIAN   OR  DEVONIAN  FORESTS, 


103 


from  the  one  to  the  other,  the  species  are  for  the  most  part  differ- 
ent, and  new  generic  fonns  are  met  with,  and,  as  I  have  elsewhere 
shown,  the  physical  conditions  of  the  two  periods  were  essentially 
different.* 

It  is,  however,  to  be  observed  that  since — as  Stur  and  others  have 
shown — Calamites  radiatus,  and  other  fonns  distinctively  Devonian 
in  America,  occur  in  Europe  in  the  Lower  Carboniferous,  it  is  not 
unlikely  that  the  Devonian  flora,  like  that  of  the  Tertiary,  appeared 
earlier  in  ^^uierica.  It  is  also  probable,  as  I  hjrve  shown  in  the  "  Re- 
ports "  already  referred  to,  that  it  appeared  earlier  in  the  Arctic  than 
in  the  temperate  zone.  Hence  an  Arctic  or  American  flora,  really 
Devonian,  may  readily  be  mistaken  for  Lower  Carboniferous  by  a 
botanist  basing  his  calculations  on  the  fossils  of  temperate  Europe. 
Even  in  America  itself,  it  would  appear,  from  recent  discoveries  in 
Virginia  and  Ohio,  that  certain  Devonian  forms  lingered  longer  in 
those  regions  than  farther  to  the  northeast ;  f  and  it  would  not  be 
surprising  if  similar  plants  occurred  in  later  beds  in  Devonshire  or 
in  the  south  of  Europe  than  in  Scotland.  Still,  these  facts,  properly 
understood,  do  net  invalidate  the  eviilence  of  fossil  plants  as  to 
geological  age,  though  errors  arising  from  the  neglect  of  them  are 
still  current. 

VI. — Geological  Relatioxs  op  some  Plant-bearing  Beds  of 
Eastern  Canada.    ("  Report  on  Erian  Plants,"  18TL) 

The  Gasp'^  sandstones  have  been  fully  described  by  Sir  W.  E. 
Logan,  in  his  "  Report  on  the  Geology  of  Canada,"  1863.  He  there 
assigns  to  them  a  thickness  of  seven  thousand  and  thirty-six  feet, 
and  shows  that  they  rest  conformably  on  the  Upper  Silurian  lime- 
stones of  the  Lower  Helderberg  group  (Ludlow),  and  are  in  their 
turn  overlaid  unconformably  by  the  conglomerates  which  form  the 
base  of  the  Carboniferous  rocks  of  New  Brunswick.  I  shall  add 
here  merely  a  few  remarks  on  points  in  their  physical  character 
connected  with  the  occurrence  ^l  plants  in  them. 

Prototaxites  {Nematophyton)  Logani  and  other  characteristic 
Lower  Erian  plants  occur  in  the  base  of  the  sandstones  at  Little 
Gaspe.  This  fact,  along  with  the  occurrence,  as  stated  in  my  paper 
of  1803,  of  rhizomes  of  Psiluphyton  preserving  their  scalariform 


*  "  Reports  on  Devonian  Plants  and  Lower  Carboniferous  Plants  of 
Canada." 

•f  Andrews,  "  Palaeontology  of  Ohio,"  vol.  ii. ;  Meek,  "  Fossil  Plants 
from  Western  Virginia,"  Philosophical  Society,  Washington,  1875. 


!l 


i      i! 


i^    ^i 


104 


TUE  GEOLOGICAL   HISTORY  OF  PLANTS. 


structure,  in  the  upper  part  of  the  marine  Upper  Silurian  lime- 
stones,* proves  the  flora  of  the  Devonian  rocks  to  have  had  its 
beginning  at  least  in  the  previous'  geological  period,  and  to  charac- 
terise the  lower  as  well  as  the  upper  beds  of  the  Devonian  series.  In 
this  connection  I  may  state  that,  from  their  marine  fossils,  as  well 
as  their  stratigraphical  arrangement,  Sir  W.  E.  Logan  and  Mr. 
Billings  regard  the  lower  portions  of  the  Gaspe  sandstones  as  the 
equivalents  of  the  Oriskany  sandstone  of  New  York.  On  the  other 
hand,  the  great  thickness  of  this  formation,  the  absence  of  Lower 
Devonian  fossils  from  its  upper  part,  and  the  resemblance  of  the 
upper  beds  to  those  of  the  newer  members  of  the  Devonian  else- 
where, render  it  probable  that  the  Gaspe  sandstones,  though  defi- 
cient in  the  calcareous  members  of  the  system,  seen  farther  to  the 
westward,  represent  the  whole  of  the  Devonian  period. 

The  Gaspe  sandstones,  as  their  name  imports,  are  predominantly 
arenaceous,  and  often  coarsely  so,  the  sandstones  being  frequently 
composed  of  large  grains  and  studded  with  quartz-pebbles.  Grey 
and  bufif  are  prevalent  colours,  but  red  beds  also  occur,  more  espe- 
cially in  the  upper  portion.  There  are  also  interstratifted  shaly 
beds,  sometimes  occurring  in  groups  of  considerable  thickness,  and 
associated  with  fine-grained  and  laminated  argillaceous  sandstone, 
the  whole  having  in  many  places  the  lithological  aspect  of  the  coal- 
measures.  At  one  place,  near  the  middle  of  the  series,  there  is  a 
bed  of  coal  from  one  inch  to  three  inches  in  thickness,  associated 
with  highly  bituminous  shales  abounding  in  remains  of  plants,  and 
also  containing  fragments  of  cristaceans  and  fishes  (Pferygofiis, 
Ctenacanthus  f  &e,).  The  beds  connected  with  this  coal  are  grey 
sandstones  and  grey  and  dark  shales,  much  resembling  those  of  the 
ordinary  coal  formation.  The  coal  is  shining  and  laminated,  and 
both  its  roof  and  floor  consist  of  laminated  bituminous  shale  with 
fragments  of  Psilophyton,  It  has  no  true  under-clay,  and  has  been, 
I  believe,  a  peaty  jnass  of  rhizomes  of  Psilophyton.  It  occurs  near 
Tar  Point,  on  the  south  side  of  Gaspe  Bay,  a  place  so  named  from 
the  occurrence  of  a  thick  dyke  of  trap  holding  petroleum  in  its 
cavities.  The  coal  is  of  considerable  horizontal  extent,  as  in  its  line 
of  strike  a  similar  bed  has  been  discovered  on  the  Douglas  River, 
about  four  miles  distant.    It  has  not  been  recognised  on  the  north 

*  The  marine  fossils  of  these  beds  have  been  determined  by  Mr. 
Billins^s.  They  are  Upper  Silurian,  with  an  intermixture  of  Lower  Devo- 
nian in  the  upper  jjart.  Fragments  of  Nematophyton  occur  in  beds  of 
the  same  age  in  the  Bay  des  Chaleurs,  at  Cape  Bon  Ami. 


THE  BRIAN  OR  DEVONIAN  FORESTS. 


105 


side  of  the  bay,  though  we  find  there  beds,  probably  on  very  nearly 
the  same  horizon,  holding  Fsilophyfoti  in  situ. 

As  an  illustration  of  one  of  the  groups  of  shaly  beds,  and  of  the 
occurrence  of  roots  of  Psilophyton,  I  may  give  the  following  sec- 
tional list  of  beds  seen  near  "  Watering  Brook,"  on  the  north  shore 
of  the  bay.    The  order  is  descending : 

FT.      IN. 

1.  Grey  sandstones  and  reddish  pebbly  sandstone  of  great 

thickness 

2.  Bright-red  shale 8     0 

3.  Grey  shales  with  stems  of  FsUophyton,  very  abundant 

but  badly  preserved 0     5 

4.  Grey  incoherent  clay,  slickensidcd,  and  with  many 

rhizomes  and  roots  of  Pfdlophytoii 0     3 

'     5.  Ilard  grey  clay  or  shale,  with  fragments  and  roots  of 

Psilophylon 4     0 

6.  Red  shale 8    0 

7.  Grey  and  reddish  crumbling  sandstone 

■  Groups  of  beds  similar  to  the  above,  but  frequently  much  more 
rich  in  fossils,  occur  in  many  parts  of  the  section,  and  evidently  in- 
clude fossil  soils  of  the  nature  of  under-clays,  on  which  little  else 
appears  to  have  grown  than  a  densci  herbage  of  Psilophyton,  along 
with  plants  of  the  genus  Arthrostigma. 

In  addition  to  these  shaly  groups,  there  are  numerous  examples 
of  beds  of  shale  of  small  thickness  included  in  coarse  sandstones, 
and  these  beds  often  occur  in  detached  fragments,  as  if  the  rem- 
nants of  more  continuous  layers  partially  removed  by  currents  of 
water.  It  is  deserving  of  notice  that  nearly  all  these  patches  of 
shale  are  interlaced  with  roots  or  stems  of  Psilophyton,  which  some- 
times project  beyond  their  limits  into  the  sandstone,  as  if  the  vege- 
table fibres  had  preserved  the  clay  from  removal.  In  short,  these 
lines  of  patches  of  shale  seem  to  be  remnants  of  soils  on  which 
Psilophyton  has  flourished  abundantly,  and  which  have  been  par- 
tially swept  away  by  the  currents  which  deposited  tlie  sand.  Some 
of  the  smaller  patches  may  even  be  fragments  of  tough  swamp  soils 
interwoven  witli  roots,  drifted  by  the  agency  of  the  waves  or  possibly 
by  ice ;  such  masses  are  often  moved  in  this  way  on  the  borders  of 
modern  swamps  on  the  sea-coast. 

The  only  remaining  point  connected  with  local  geology  to  which 

I  shall  allude  is  the  admirable  facilities  afforded  by  the  Gaspe  coast 

both  for  ascertaining  the  true  geological  relations  of  the  beds,  and 

for  studying  the  Devonian  plants,  as  distinctly  exposed  on  large  sur- 

11 


r 


106 


TUE  GEO'    '^.ICAL   HISTORY   OF  PLANTS. 


faces  of  rock.     On  coast  of  thp  river  St.  Lawrence,  at  Cape 

Rozier  and  its  vicim.y,  the  Lower  Silurian  rocks  of  the  Quebec 
group  are  well  exposed,  and  are  overlaid  unconformably  by  the  mas- 
sive Upper  Silurian  limestones  of  Cape  Gaspe,  which  rise  into  cliflFs 
six  hundred  feet  in  height,  and  can  be  seen  filled  with  their  char- 
acteristic fossils  on  both  sides  of  the  cape.  Resting  upon  these,  and 
dipping  at  high  angles  toward  Gaspe  Bay,  are  the  Devonian  sand- 
stones, which  are  exposed  in  rugged  cliffs  slightly  oblique  to  their 
line  of  strike,  along  a  coast-line  of  ten  miles  in  length,  to  the  head 
of  the  bay.  On  the  opposite  side  of  the  bay  they  reappear ;  and, 
thrown  into  slight  undulations  by  three  anticlinal  curves,  occupy 
a  line  of  coast  fifteen  miles  in  length.  The  perfect  manner  in  which 
the  plant-bearing  beds  are  exposed  in  these  fine  natural  sections  may 
serve  to  account  for  the  completeness  with  which  the  forms  and 
habits  of  growth  of  the  more  abundant  species  can  be  described. 

In  the  Bay  des  Chaleurs.  similar  rocks  exist  with  some  local 
variations.  In  the  vicinity  of  Campbellton  are  calcareous  and  mag- 
nesian  breccia  or  agglomerate,  hard  shales,  conglomerates  and  sand- 
stones of  Lower  Devonian  age.  The  agglomerate  and  lower  shales 
contain  abundant  remains  of  fishes  of  the  genera  Cepliolaspis,  Coc- 
costeus,  Ctenacanihus,  and  HomacanthuH,  and  also  fragments  of 
Ptcrygohis.  The  shales  and  sandstones  aboi;nd  in  remains  of  Psilo- 
phyton,  with  which  are  Nematophyton,  Arthrostigma,  and  Lepto- 
phleum  of  the  same  species  found  in  the  Lower  Devonian  of  Gaspe 
Bay.  These  beds  near  Campbellton  dip  to  the  northward,  and  the 
Restigouche  River  here  occupies  a  synclinal,  for  on  the  opposite  side, 
at  Bordeaux  Quarry,  there  are  thick  beds  of  grey  sandstone  dip{)ing 
to  the  southward,  and  containing  large  silicified  trunks  of  I^oto- 
taxites,  in  addition  to  Psilophyton.  These  beds  are  all  undoubtedly 
Lower  Brian,  but  farther  to  the  eastward,  on  the  north  side  of  the 
river,  there  are  newer  and  overlying  strata.  These  are  best  seen  at 
Scaumenac  Bay,  opposite  Dalhousie,  between  Cape  Florissant  and 
Maguacha  Point,  where  they  consist  of  laminated  and  fine-grained 
sandstone,  with  shales  of  grey  colours,  but  holding  some  reddish  beds 
at  top,  and  overlaid  unconformably  by  a  great  thickness  of  Lower 
Carboniferous  red  conglomerate  and  sandstone.  In  these  beds  nu- 
merous fossil  fishes  have  been  found,  among  which  Mr.  Whiteaves 
recognises  species  of  Picrichthys,  Glyptolepis,  Cheirolepis,  &c.  With 
these  are  found  somewhat  plentifully  four  species  of  fossil  ferns,  all 
of  Upper  Brian  types,  of  which  one  is  peculiar  to  this  locality;  but 
the  others  are  found  in  the  Upper  Brian  of  Perry,  in  Maine,  or  in 
the  Catskill  group  of  New  York. 


I 


THE  BRIAN   OR  DEVONIAN  FORESTS. 


107 


In  order  that  distinct  notions  may  be  conveyed  as  to  the  geo- 
logical horizons  of  the  species,  I  may  state  that  the  typical  Devonian 
or  Brian  scries  of  Canada  and  New  York  may  Iw  divided  in  descend- 
ing order  into — 1.  T':e  Chemung  group,  including  the  Chemung  and 
Portage  sandstones  and  shales.  2.  The  Hamilton  group,  including 
the  Genesee,  Hamilton,  and  IMarcellus  shales.  3.  The  Corniferous 
limestone  and  its  associated  beds.  4.  The  Oriskany  sandstone.  As 
the  Corniferous  limestone,  which  is  the  equivalent  of  the  Lower 
Carboniferous  limestone  in  the  Carboniferous  period,  is  marine,  and 
affords  scarcely  any  plants,  we  may,  as  is  usually  done  for  like  pur- 
poses in  the  Carboniferous,  group  it  with  the  Oriskany  under  the 
name  Lower  Erian.  The  Hamilton  rocks  will  then  be  Middle  Erian, 
and  the  Chemung  group  Upper  Erian.  In  the  present  state  of  our 
knowledge,  the  series  may  be  co-ordinated  with  the  rocks  of  Gaspe, 
New  Brunswick,  and  Maine,  as  in  the  following  table : 


Subdinsions. 

New  York 

and 

Western  Oanada. 

Gasp6 

and  Hay  des 

Chaleurs. 

Southern 

New 
Brunswick. 

Coast 

of 
Maine. 

Upper 
Devonian  or 

Chemung 
Group. 

Upper 
Sandstones. 

MispecGroup. 
Shale,  Sand- 

Perry Sand- 
stones. 

Erian. 

Long  Cove,  &c. 

Scauminac 

Beds. 

stone,  and 
Conglomer- 
ate. 

Middle 

Hamilton 

Middle 

LittleR.Group 

. 

Devonian  or 
Brian. 

Group. 

Sandstones. 

Bois  Brul6, 

Cape  Oiseau, 

(including 

Cordaite 

Shales  and 

• 

&c. 

Uadoxylon 
Sandstone). 

Lower 

Corniferous 

Lower 

Lower  Con- 

Devonian or 

and 

Sandstones. 

glomerates, 

Brian. 

Oriskany 
groupa." 

Gaspe  Basin, 
Little  Gasp6, 

&c. 

Campbellton 

Beds. 

&c. 

It  may  be  proper,  before  closing  this  note,  to  state  the  reasons 
which  have  induced  me  to  suggest  in  the  following  pages  the  use  of 
the  term  "  Erian,"  as  equivalent  to  "  Devonian,"  for  the  great  sys- 
tem of  formations  intervening  between  the  Upper  Silurian  and  the 
Lower  Carboniferous  in  America.  1  have  been  induced  to  adopt 
this  course  by  the  following  considerations:  1.  The  great  area  of 


1 : 


108 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


II 


II 


undisturbed  and  unaltered  rocks  of  this  age,  including  a  thickness 
in  some  places  of  eighteen  thousand  feet,  and  extending  from  east 
to  west  through  the  Northern  States  of  the  Union  and  western 
Canada  for  nearly  seven  hundred  miles,  while  it  spreads  from  north 
to  south  from  the  northern  part  of  Michigan  far  into  the  Middle 
States,  is  undoubtedly  the  most  important  Devonian  area  now  known 
to  geologists.  2.  This  area  has  been  taken  by  all  American  geolo- 
gists as  their  typical  Devonian  region.  It  is  rich  in  fossils,  and 
these  have  been  thoroughly  studied  and  admirably  illustrated  by 
the  Ne-.y  York  and  Canadian  Surveys.  3.  The  rocks  of  this  area 
surround  the  basin  of  Lake  Erie,  and  were  named,  in  the  original 
reports  of  the  New  York  Survey,  the  "  Urie  Division."  4.  Great 
difficulties  have  been  experienced  in  the  classification  of  the  Euro- 
pean Devonian,  and  the  uncertainties  thus  arising  have  tended  to 
throw  doubt  on  the  results  obtained  in  America  in  circumstances  in 
which  such  difficulties  do  not  occur. 

These  reasons  are,  I  think,  sufficient  to  warrant  me  in  holding 
the  great  Erie  Division  of  the  New  York  geologists  as  the  typical 
representative  of  the  rocks  deposited  between  the  close  of  the  Upper 
Silurian  and  the  beginning  of  the  Carboniferous  period,  and  to  us< 
the  term  Enan  as  the  designation  of  this  great  series  of  deposits  a. 
developed  in  America,  in  so  far  at  least  as  their  flora  is  concerned. 
In  doing  so,  I  do  not  wish  to  introduce  a  new  name  merely  for  the 
sake  of  novelty  ;  but  I  hope  to  keep  before  the  minds  of  geologists 
the  caution  that  they  should  not  measure  the  Erian  formations  of 
America,  or  the  fossils  which  they  contain,  by  the  comparatively 
depauperated  representatives  of  this  portion  of  the  geological  scale 
in  the  Devonian  of  western  Europe. 


VII. — On  the  Relations 
Bear  Island  with 
America. 


OP    THE    so-galled 

THE    Paleozoic 


"Ursa  Stage"  op 
Flora    of    North 


The  following  note  is  a  verbatim  copy  of  that  published  by  me 
in  1873,  and  the  accuracy  of  which  has  now  been  vindicated  by  the 
recent  observations  of  Nathorst : 

The  plants  catalogued  by  Dr.  Heer,  and  characterising  what  he 
calls  the  "  Ursa  Stage,"  are  in  part  representatives  of  those  of  the 
American  flora  which  I  have  described  as  the  "  Lower  Carboniferous 
Coal-Measuros  "  (Subearboniferous  of  Dana),  and  whose  characteristic 
species,  as  developed  in  Nova  Scotia,  I  noticed  in  the  "  Journal  of 
the  Geological  Society  "  in  1858  (vol.  xv.).  Dr.  Heer's  list,  however, 
includes  some  Upper  Devonian  forms ;  and  I  would  suggest  that 


THE  BRIAN   OR  DEVONIAN  FORESTS. 


109 


either  the  plants  of  two  distinct  beds,  one  Lower  Carboniferous  and 
the  other  Upper  Devonian,  have  been  near  to  or  in  contact  with  each 
other  and  have  been  intermixed,  or  else  that  in  this  high  northern 
latitude,  in  which  (for  reasons  stated  in  my  "  Report  on  the  Devo- 
nian Flora"*)  I  believe  the  Devonian  plants  to  have  originated,  there 
was  an  actual  intermixture  of  tlie  two  floras.  In  America,  at  the 
base  of  the  Carbouifcrous  of  Ohio,  a  transition  of  this  kind  seems 
to  occur;  but  elsewhere  in  northeastern  America  the  Lower  Car- 
boniferous plants  are  usually  unmixed  with  the  Devonian. 

Dr.  Ileer,  however,  proceeds  to  identify  these  plants  with  those 
of  the  American  Chemung,  and  even  with  those  of  the  Middle  De- 
vonian of  New  Brunswick,  as  described  by  me — a  conclusion  from 
which  I  must  altogether  dissent,  inasmuch  as  the  latter  belong  to 
beds  which  were  disturbed  and  jiartially  metamorphosed  before  the 
deposition  of  the  lowest  Carboniferous  or  "  Subearboniferous  "  beds. 

Dr.  Pleer's  error  seems  to  have  arisen  from  want  of  acquaintance 
with  the  rich  flora  of  the  Middle  Devonian,  which,  while  differing  in 
species,  has  much  resemblance  in  its  general  facies,  and  especially  in 
its  richness  in  ferns,  to  that  of  the  coal-formation. 

To  geologists  acqiiaintcd  with  the  stratigraphy  and  the  accom- 
panying animal  fossils.  Dr.  Heer's  conclusions  will  of  course  appear 
untenable ;  but  they  may  regard  them  as  invalidating  the  evidence 
of  fossil  plants ;  and  for  this  reason  it  is,  I  think,  desirable  to  give 
publicity  to  the  above  statements. 

I  consider  the  British  equivalent  of  the  lower  coal-measures  of 
eastern  America  to  be  the  lower  limestone  shales,  the  Tioeedian 
group  of  Mr.  Tate  (1858).  but  which  have  sometimes  been  called  the 
"  Calciferous  Sandstone  "  (a  name  preoccupied  for  a  Cambrian  group 
in  America).  This  group  does  not  constitute  "  beds  oi  passage  "  to 
the  Devonian,  more  especially  in  eastern  America,  where  the  lower 
coal-formation  rests  unconformably  on  the  Devonian,  and  is  broadly 
distinguished  by  its  fossils. 

The  above  notes  would  not  have  been  extended  to  so  great 
length,  but  for  the  importance  of  the  Erian  flora  as  the  precursor 
of  that  of  the  Carboniferous,  and  the  small  amount  of  attention 
hitherto  given  to  it  by  geologists  and  botanists. 

*  "  Geological  Survey  of  Canada,"  18Y1. 


hi 


Il!i4 


CHAPTER  IV. 

THE  CARBONIFEROUS   FLORA — CULMINATION   OF  THE 
ACROQENS — FORMATION   OF  COAL. 

Ascending  from  the  Erian  to  the  Carboniferous  sys- 
tem, so  called  because  it  contains  the  greatest  deposits  of 
anthracite  and  bituminous  coal,  we  are  still  within  the 
limits  of  the  Palaeozoic  period.  We  are  still  within  the 
reign  .of  the  gigantic  club-mosses,  cordaites,  and  taxine 
pines.  At  the  close  of  the  Erian  there  had  been  over 
the  whole  northern  hemisphere  great  changes  of  level, 
accompanied  by  active  volcanic  phenomena,  and  under 
these  influences  the  land  flora  seems  to  have  much  dimin- 
ished. At  length  all  the  old  Erian  species  had  become 
extinct,  and  their  place  was  supplied  by  a  meagre  group 
of  lycopods,  ferns,  and  pines  of  different  species  from 
those  of  the  preceding  Erian.  This  is  the  flora  of  the 
Lower  Carboniferous  series,  the  Tweedian  of  England, 
the  Horton  series  of  Nova  Scotia,  the  lower  coal-meas- 
ures of  Virginia,  the  culm  of  Germany.  But  the  land 
again  subsided,  and  the  period  of  the  marine  limestone 
of  the  Lower  Carboniferous  was  introduced.  In  this  the 
older  flora  disappeared,  and  when  the  land  emerged  we 
find  it  covered  with  the  rich  flora  of  the  coal-forniation 
proper,  in  which  the  great  tribes  of  the  lycopods  and 
cordaites  attained  their  maxima,  and  the  ferns  were  con- 
tinued as  before,  though  under  new  generic  and  specific 
forms. 


T 


■    ! 


THE  CARBONIFEROUS  FLORA. 


Ill 


There  is  something  very  striking  in  this  snccession  of 
a  new  plant  world  without  any  material  advance.  It  is 
like  passing  in  the  modern  world  from  one  district  to 
another,  in  which  we  see  the  same  forms  of  life,  only 
represented  by  distinct  though  allied  species.  Thus,  when 
the  voyager  crosses  the  Atlantic  from  Europe  to  Amer- 
ica, he  meets  with  pines, 
oaks,  birches,  poplars, 
and  beeches  of  the  same 
genera  with  those  he 
had  left  behind  ;  but 
the  species  are  distinct. 
It  is  something  like  this 
that  meets  us  in  our  as- 
cent into  the  Carbonif- 
erous world  of  plants. 
Yet  we  know  that  this 
is  a  succession  in  time, 
that  all  our  old  Erian 
friends  are  dead  and 
buried  long  ago,  and 
that  these  are  new  forms 
lately  introduced  (Fig. 
32). 

Conveying  ourselves, 
then,  in  imagination  for- 
ward to  the  time  when 
our  greatest   accumula- 


a  h  c  d  e  f  g 

Fio.  32. —  Foliage  from  the  coal-for- 
mation, a,  Alethopteru  lonchitica, 
fern  (Moose  River),  h,  Sphenophyl- 
lum  cSchlotheimii  (Pictou).  c,  Lepi- 
dodendron  binerve  (Sydney),  rf,  As- 
terophyllites  foliosa  (?)  (Sydney), 
«,  Cordttitea  (Jojif^ns).  /,  Ifeiirop- 
teris  rarinervis^  fern  (Sydney). 
g,  Odoniopteris  suhcuneata,  fern 
^Sydney). 


tionsof  coal  were  formed, 
and  fancying  that  we  are  introduced  to  the  Ameri- 
can or  European  continent  of  that  period,  we  find  our- 
selves in  a  new  and  strange  world.  In  the  Devonian 
age,  and  even  in  the  succeeding  Lower  Carboniferous, 
there  was  in  the  interior  of  America  a  wide  inland  sea, 
with  forest  belts  clinging  to  its  sides  or  clothing  its  isl- 
ands.    But  in  the  coal  period  this  inland  sea  had  given 


!'• 


II 

1 

-  ff 

M  ' 

1  i 

1  ^ 

!  i  ' 

1 

112 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


place  to  vast  swampy  flats,  and  which,  instead  of  the  oil- 
bearing  shales  of  the  Brian,  were  destined  to  produce 
those  immense  and  wide-spread  accumulations  of  vege- 
table matter  which  constitute  our  present  beds  of  bitu- 
minous and  anthracite  coal.  The 
atmosi)here  of  these  great  swamps 
is  moist  and  warm.  Their  vege- 
tation is  most  exuberant,  but  of 
forms  unfamiliar  to  modern  eyes, 
and  they  swarm  with  insects, 
millepedes,  and  scorpions,  and 
with  batrachian  reptiles  large 
and  small,  among  which  we  look 
in  vain  for  representatives  of  the 
birds  and  beasts  of  the  present 
day. 

Prominent  among  the  more 
gigantic  trees  of  these  swampy 
forests  are  those  known  to  us  as 
Sigillarim  (Fig.  33).  They  have 
tall,  pillar-like  trunks,  often  sev- 
eral feet  in  diameter,  ribbed  like 
fluted  columns,  but  in  the  re- 
verse way,  and  spreading  at  the 
top  into  a  few  thick  branches, 
which  are  clothed  with  long, 
grass-like  leaves.  They  resem- 
ble in  some  respects  the  Lepi- 
dodendra  of  the  Erian  age,  but 
are  more  massive,  with  ribbed  in- 
stead of  scaly  trunks,  and  longer 
leaves.  If  we  approach  one  of 
them  more  closely,  we  are  struck  with  the  regular  ribs  of 
its  trunk,  dotted  with  rows  of  scars  of  fallen  leaves,  from 
which  it  receives  its  name  Sigillaria,  or  seal-tree  (Figs. 
34-37).     If  we  cut  into  its  stem,  we  find  that,  instead  of 


Fio.  33. — Siaillarice,  restored. 

A,  SigUtaria  Brownii. 

B,  aigiUaria  eleffans. 


THE  CARBONIFEROUS  FLORA. 


113 


tlio  thin  bark  and  firm  wood  with  which  we  are  familiar 
in  our  modern  trees,  it  has  a  hard  external  rind,  tlien  a 
great  thickness  of  cellular  matter  with  rope-like  bands  of 
fibres',  constituting  an  inner  bark,  while  in  the  centre  is 
a  firm,  woody  axis  of  comparatively  Bmall  diameter,  and 


Qj;:« 


Fio.  84. — Sigillaria  Lonvaynna,  Dawson.    «,  Zones  of  fruit-sciirt*.   b,  Laaf- 
Bcar  enlarged,     c,  i'ruit-scar  enlarged.    See  appended  note. 

somewhat  intermediate  in  its  structures  between  that  of 
the  Lepidodendra  and  those  of  the  cycads  and  the  taxine 
conifers.  Thus  a  great  stem,  five  feet  in  diameter,  may 
consist  principally  of  cellular  and  bast  fibres  with  very 
little  true  woody  matter.     The  roots  of  this  tree  are 


|S 


I*' 


M! 


114 


THE  GEOLOGICAL  IILSTORY  OF  PLANTS. 


perhaps  its  most  sinj^ular  feature.  They  usually  start 
from  the  stem  in  four  main  branches,  then  regularly 
bifurcate  several   times,  and  then   run   out  into  great 


Fio.  35. — Stem  of  Siffillaria     Fio.  80. — Two  ribs  of  Siffillaria  Brownii. 
Jirownii,  reduciid.  Natural  size. 

cylindrical  cables,  running  for  a  long  distance,  and  evi- 
dently intended  to  anchor  the  plant  firmly  in  a  soft  and 

oozy  soil.  They  were  furnished 
with  long,  cylindrical  rootlets 
placed  regularly  in  a  spiral  man- 
ner, and  so  articulated  that  when 
they  dropped  ofif  they  left  regu- 
lar rounded  scars.  They  are, 
in  short,  the  Stigmariw,  which 
we  have  already  met  witli  in 
the  Brian  (Figs.  38,  39).  In 
Fig.  33  I  have  endeavoured  to 
restore  these  strange  trees.  It  is 
not  wonderful  that  such  plants 
have  caused  much  botanical  con- 
Fio.  37.-Portion  of  lower    trovcrsy.    It  was  long  before  bot- 

part  ot  stem  ol  iS.  Brownn.  •'       ,,,  .         i.ii 

Natural  size.  anists  could  be  conviuced  that 


THE  CAIIBONIFEUOUS  FLORA. 


115 


their  roots  are    properly   roots   at  all,   and   not  stems 
of  some  aquatic   i)lant.      Thou   tlio  structure  of  their 


Flo.  88. — atigmaria  root,  seen  i  om  almvc,  nhowing  its  regular  divisions. 
From  "Acadiun  Geolof^y." 

stems  its  most  puzzlin*^,  and  their  fruit  is  an  cni<^ma, 
for  while  some  have  found  connected  with  them  cones 
supposed  to  resemble  those  of 
lycopods,    others    attribute    to 
them  fruits  like  those  of  vew- 
trees.     For  years   I  have  been 
myself  gathering  materials  from 
the  rich  coal-formation  deposits 
of  Nova  Scotia  in   aid  of   the 
solution  of  these  questions,  and 
in  the  mean  time  Dr.  William- 
son, of  Manchester,  and  Renault 
and  other  botanists  in  France, 
have  been  amassing  and  study- 
ing stores  of  specimens,  and  it 
is  still  uncertain  who  may  final- 
ly be  the  fortunate   discoverer 
to  set  all  controversies  at  rest, 
that  the  true  solution  consists  in  the  fact  that  there  are 
many  kinds  of  Sigillarice.     While  in  the  modern  forests 


Fiu.  39. — Portion  of  bark  of 
Stigmaria,  Hhowinj^  scars 
of  attachment  of  rootlets. 


My  present  belief  is, 


116 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


of  America  and  Europe  the  species  of  any  of  our  ordinary 
trees,  as  oaks,  birches,  or  maples,  may  ahnost  be  counted 
on  one's  fingers,  Schimper  in  his  vegetable  palaeontology 
enumerates  about  eighty  species  of  Carboniferous  Sigil- 
laricB  ;  and  while  on  the  one  hand  many  of  these  uie  so 
imperfectly  known  that  they  may  be  regarded  as  uncer- 
tain, on  the  other  hand  many  species  must  yet  remain  to 
be  discovered.*  Now,  in  so  vast  a  number  of  species 
there  must  bo  a  great  range  of  organisation,  and,  indeed, 
it  has  already  been  attempted  to  subdivide  them  into 
several  generic  groups.  The  present  state  of  tlie  question 
appears  to  me  to  be  this,  that  in  these  SigillaricB  we  have 
a  group  divisible  into  several  forms,  some  of  which  will 
eventually  be  classed  with  the  Lepidodendra  as  lycopods, 
while  others  will  be  found  to  be  naked-seeded  phaeno- 
gams,  allied  to  the  pines  and  cycacxs,  and  to  a  remarkable 
group  of  trees  known  as  Cordaites,  which  we  must  shortly 
notice. 

Before  considering  other  forms  of  Carboniferous  vege- 
tation, let  us  glance  at  the  accumulation  of  coal,  and  the 
agency  of  the  forests  of  Sigillarim  therein.  Let  us  im- 
agine, in  the  first  instance,  such  trees  as  those  represented 
in  the  figures,  growing  thickly  together  over  vast  swampy 
flats,  with  quantities  of  undergrowth  of  ferns  and  other 
plants  beneath  their  shade,  and  accumulating  from  age  to 
age  in  a  moist  soil  and  climate  a  vast  thickness  of  vege- 
table mould  and  trunks  of  trees,  and  spores  and  spore- 
cases,  and  we  have  the  conditions  necessary  for  the  growth 
of  coal.  Many  years  ago  it  was  observed  by  Sir  William 
Logan  that  in  the  coal-field  of  South  Wales  it  was  the 
rule  with  rare  exceptions  that,  under  every  bed  of  coal, 
there  is  a  bed  of  clay  filled  with  roots  of  tlie  Stigmaria, 
already  referred  to  as  the  root  of  Sigillaria.     This  dis- 

♦  In  a  recent  memoir  (Berlin,  1887)  Stur  has  raised  tha  number  of 
species  in  one  subdivision  of  the  SigiUance  (the  Favularia)  to  forty- 
seven  ! 


THE  CARBONIFEROUS  FLORA. 


117 


covery  has  since  been  extended  to  all  the  coal-fields  of 
Europe  and  America,  and  it  is  a  perfectly  conclusive  fact 
as  regards  the  origin  of  coal.  Each  of  these  "under- 
clays,"  as  they  are  called,  must,  in  fact,  have  been  a  soil 
on  which  grew,  in  the  first  instance,  Sigillariae  and  other 
trees  having  stigmaria-roots.  Thus,  the  growth  of  a 
forest  of  SigillaricB  was  the  first  step  toward  the  accumu- 
lation of  a  bed  of  coal.  More  than  this,  in  some  of  the 
coarser  and  more  impure  coals,  where  there  has  been 
sufficient  earthy  matter  to  separate  and  preserve  impres- 
sions of  vegetable  forms,  we  can  see  that  the  mass  of  the 
coal  is  made  up  of  flattened  Sifjillarim,  mixed  with  vege- 


Pio.  40. — Vegetable  tissues  from  coal,    a,  Sigillaria  and  Cordaites. 

b,  Calamodendron. 

table  debris  of  all  kinds,  including  sometimes  vast  quan- 
tities of  Icpidodendroid  spores,  and  the  microscopic  study 
of  the  coal  gives  similar  results  (Fig.  40).  Further,  on 
the  surfaces  of  many  coals,  and  penetrating  the  shales  or 
sandstones  which  form  tlieir  roofs,  we  find  erect  stumps 
of  bigillaria  and  other  trees,  showing  that  the  accumula- 
tion of  the  coal  terminated  as  it  had  begun,  by  a  forest- 
growth.  I  introduce  here  a  section  of  a  few  of  the  nu- 
merous beds  of  coal  exposed  in  the  cliffs  of  the  South 
Joggins,  in  Nova  Scotia,  in  illustration  cf  these  facts. 
We  can  thus  see  how  in  the  slowly  subsiding  areas  of  the 
coal-swamps  successive  beds  of  coal  were  accumulated, 
alternating  witii  beds  of  sandstone  and  shale  (Figs.  41, 
42).  For  other  details  of  this  kind  I  must  refer  to 
papers  mentioned  in  the  sequel. 

12  " 


118 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


Returning  to  tlic  more  special  subject  of  this  work,  I 
may  remark  that  the  lepidodendroid  trees  ana  the  ferns, 
both  the  arborescent  and  herbaceous  kinds,  are  even  more 
richly  represented  in  the  Carboniferous  than  in  the  pre- 
ceding Erian.  I  must,  however,  content  myself  with 
merely  introducing  a   few   representatives    of  some  of 

the  more  common 


kinds,  in  an  ap- 
pended note,  and 
here  give  a  figure 
of  a  well-known 
Lower  Carbonifer- 
ous l.epi  iodendron, 
with  its  various 
forms  of  leaf-bases, 
and  its  foliage  and 
fruit  (Fig.  43),  and 
a  similar  illustra- 
tion of  an  allied 
generic  form,  that 
known  as  LepidO' 
phloios*  (Fig.  44). 
Another  group 
which  claims  our 
attention  is  that 
of  the  Calamites. 
These  are  tall,  cy- 
lindrical, branch- 
less stems,  with 
whorls  of  branch- 
lets,  bearing  need  le- 
like  leaves  and  spreading  in  stools  from  the  base,  so  as  to 
form  dense  thickets,  like  Southern  cane-brakes  (Fig.  4G). 
They  bear,  in  habit  of  growth  and  fructification,  a  close 


Fig.  41. — Rods  associated  witli  the  main  coal 
(S.  Jogffins,  Nova  Scotia).  1,  Shiilc  and  sand- 
stone—plants with  Spirorhis  attached;  rain- 
marks  («.).  (2,  Sandstone  and  shale,  eight 
feet — erect  Calamites\  3,  Gray  sandstone, 
Beven  feet ;  4,  Gray  shale,  four  teet — an  erect 
coniferous  (h  tree,  rooted  on  the  shale,  passes 
up  through  fifteen  feet  of  the  sandstones  and 
shale.)  5,  Gray  sandstone,  four  feet.  6,  Gray 
shale,  six  inches — prostrate  and  erect  trees, 
with  rootlets,  leaves,  A'aiadites^  and  Spiror- 
bis  on  the  plants.  7,  Main  coal-seam,  five 
feet  of  coal  in  two  scams.  8,  Undorclay,  with 
rootlets. 


*  For  full  descriptions  of  those,  see  "  Acadian  Geology." 


THE  CARBONIFEROUS  FLORA. 


119 


relation  to  our  modern  equisetnms,  or  mare's- tails,  but, 
as  in  other  cases  wo  have  met  with,  are  of  gigantic  size 
and  comparatively  complex  structure.  Their  stems,  in 
cross-section,  show  radi- 
ating bundles  of  fibres, 
like  those  of  exogenous 
woods,  yet  the  whole  plan 
of  structure  presents  some 
curious  resemblances  to 
the  stems  of  their  hum- 
ble successors,  the  mod- 
ern mare's-tails.  It  would 
seem,  from  the  manner 
in  which  dense  brakes  of 
these  Calamitcs  have  been 
preserved  in  tlie  coal-for- 
mation of  Nova  Scotia, 
that  they  spread  over  low 
and  occasionally  inun- 
dated flats,  and  formed 
fringes  on  the  seaward 
sides  of  the  great  Sigilla- 
ria  forests.  In  this  way 
they  no  doubt  contrib- 
uted to  prevent  the  invasion  of  the  areas  of  coal  ac- 
cumulation by  the  muddy  waters  of  inundations,  and 
thus,  though  they  may  not  have  furnished  much  of  the 
material  of  coal,  they  no  doubt  contributed  to  its  ])urity. 
Many  beautiful  plants  of  the  genera  AsterophylUtes  and 
Annularia  are  supposed  to  havo  beeii  allied  to  the  '^.ah- 
mitea,  or  to  have  connected  t!inr.ii  wiih  tlio  Rhizoar'ps. 
The  stems  and  fruit  of  these  plants  have  strong  points  of 
resemblance  to  those  of  SphenopJit/Ihtrn,  and  the  leaves 
are  broad,  and  not  narrow  and  angular  like  those  of  the 
true  Calamitcs  (Fig.  45). 

No  one  has  done  more  than  my  friend  Dr.  William- 


Fio.  42. — Erect  Siiiillaria,  ptai:din,gf 
on  a  coal-soam  (S.  Jogj^ang^  Novu 
Scotia). 


I  li 


i 


7  • 


I 


I : 

i  ; 


120  THE  GEOLOGICAL  HISTORY  OF  PLANTS. 

T 


Fio.  43. — Lepidodendron  corru(/atum,  Dawson,  a  tree  characteristic  of  the 
Lower  Carboniferous,  a,  liestoration.  b.  Leaf,  natural  size  o,  Cone 
and  branch,  d,  Branch  and  leaves,  e.  Various  forms  of  Icaf-arcoles. 
F,  Sporai)(ji>im.  i,  l,  m,  Bark,  with  leaf-soars,  n,  Bark,  with  Ical- 
Bcors  of  ol«i  stem,    o,  Decorticated  stem  {Knorriu). 


THE  CARBONIFEROUS  FLORA. 


121 


Fio.  44. — LepidophloioK  Arndianus,  Dawson,  a  Icniciodondroid  treo  of  tho 
coal-formation,  a.  Restoration,  b,  Tortion  of  hark  (two  thirds  natural 
size),  c,  Ligneous  surface  of  the  same,  f,  Cone  (two  thirds  natural  size), 
o,  Leaf  (natural  size),  k,  Portion  of  woody  cvliiider,  showitiar  outer  and 
inner  series  of  vessels  magnified,  l,  Scalaritorin  vessels  (highly  magni- 
fied).   M,  Various  forma  of  leaf-scarA  and  leaf-buses  (natural  size). 


122 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


'a 


!i 


if 


I 


■I  j 


lii 


son,  of  Manchester,  to  illustrate  the  structure  of  Cala- 
mites,  and  he  has  shown  that  these  plants,  like  other 
cryptogams  of  the  Carboniferous,  had  mostly  stems  with 
regular  fibrous  wedges,  like  those  of  exogens.  The 
structure  of  the  stem  is,  indeed,  so  complex,  and  differs 
so  much  in  different  stages  of  growth,  and  different  states 
of  preservation,  that  we  are  in  danger  of  falling  into  the 
greatest  confusion  in  classifying  these  plants.  Sometimes 
what  we  call  a  Calamite  is  a  mere  cast  of  its  pith  showing 
longitudinal  striae  and  constrictions  at  the  nodes.     Some- 


Fio.  45. — AderophijllUes,  Spheiwph>/ll<im,  and  A/uiidaria.  A,  Astero- 
phyUUes  triiierne.  a>,  Leaf  enlarjjed.  b,  Annvlaria  gphenophi/Uoidea. 
B',  Leaf  enlarged,  o,  Sphenophyllnm  erosum.  c»,  LeaHet  enlar^d. 
c»,  Scalariform  vessel  of  Sphenophyllum.  d,  Finnttlaria  ramosissima^ 
probably  a  root. 

times  we  have  the  form  of  the  outer  surface  of  the  woody 
cylinder,  showing  longitudinal  ribs,  nodes,  and  marks  of 
the  emission  of  the  branchlets.  Sometimes  we  have  the 
outer  surface  of  the  plant  covered  with  a  smooth  bark 
showing  flat  ribs,  or  almost  smooth,  and  having  at  the 
nodes  regular  articulations  with  the  bases  of  the  verticil- 


THE  CARBONIFEROUS  FLORA, 


123 


late  branchlefcs,  or  on  the  lower  part  of  the  stem  the 
marks  of  the  attachment  of  the  roots.  The  Calamites 
grew  in  dense  clumps,  budding  off  from  one  another, 
sometimes  at  different  levels,  as  the  mud  or  sand  accumu- 
lated about  tlieir  stems,  and  in  some 
species  there  were  creeping  rliizomata 
or  root-stocks  (Figs.  46  to  49). 

But  all  Calamites  were  not  alike 
in  structure.      In   a  recent  paper* 


V 


I 


V. 


Fig.  46.  —  Calamites. 
A,  C.  Suckoril.  B, 
C.  Cistii.  ( From 
"  Acadian  Geolo- 
gy-")   ^'  , 


Fio.  47.— .Erect  Cala- 
mites, witli  roots  at- 
tached (Nova  Sco- 
tia). 


Fig.  48.— Node  of  C. 
Cistii,  with  long 
leaves  (Nova  Sco- 
tlft),       , 


Dr.  Williaiuson  describes  three  distinct  structural  types. 
What  he  regards  as  typical  Calamites  has  in  its  woody 
zone  wedges  of  barred  vessels,  with  thick  bands  of  cel- 
lular tissue   separating  tliem.      A   second   type,    which 


*  "  Memoirs  of  the  Philosophical  Society,"  Manchester,  ISSS-'S?. 


^v 


I 


't  i 


.  ;:i 


1 1 


; 


iV: 


':\ 

'■'! 

-. 

'    J 

1  ^^ 

mM  ' 

H^ 

[f  - 

f 


124 


THE  GEOLOGICAL    "'^""ORY  OF  PLANTS. 


he    refers    to    Calamor'  las    woody    bundles    com- 

posed of  reticulated  altiporous   fibres,   with    their 

porous  sides  parallel  che  medullary  rays,  which  are 
better  developed  than  in  the  previous  form.  The  inter- 
vening cellular  masses  are  composed  of  elongated  cells. 
This  is  a  decided  advance  in  structure,  and  is  of  the  type 
of  those  forms  having  the  most  woody  and  largest  stems, 


(C) 


•T* 


(a) 


VAAV 


Fio.  49. — Erect  Calamites  {C.  Suckovii),  showing  the  mode  of  growth  of 
new  stems  (i),  and  different  forms  of  the  ribs  (a,  c),  (Pictou,  Nova 
Scotia.)    Half  natural  size. 

which  Brongniart  named  Calamodendron  (Fig.  50).  A 
third  form,  to  which  Dr.  Williamson  seems  to  prefer  to 
assign  this  last  name,  has  the  tissue  of  the  woody  wedges 
barred,  as  in  the  first,  but  the  medullary  rays  are  better 
developed  than  in  the  second.  In  this  third  form  the 
intermediate  tissue,  or  primary  medullary  rays,  is  truly 
fibrous,  and  with  secondary  medullary  rays  traversing  it. 
My  own  observations  lead  me  to  infer  that  there  was  a 
fourth  type  of  calamitean  stem,  less  endowed  with  woody 
matter,  and  having  a  larger  fistulous  or  cellular  cavity 
than  any  of  those  described  by  Dr.  Williamson. 

There  is  every  reason  to  believe  that  all  these  various 


THE  CARBONIFEROUS  FLORA. 


125 


and  complicated  stems  belonged  to  higher  and  nobler 
types  of  mare's-tails  tiian  those  of  the  modern  world,  and 
that  their  fructification  was  equisetaceous  and  of  the 
form  known  as  Calamostachys. 

We  have  already  seen  that  noble  tree-ferns  existed  in 
the  Erian  period,  and  these  were  continued,  and  their 
number  and  variety  greatly  extended,  in  the  Carbonifer- 
ous. In  regard  to  the  structure  of  their  stems,  and  the 
method  of  supporting  these  by  atrial  roots,  the  tree-ferns 
of  all  ages  have  been  nearly  alike,  and  the  form  and 
structure  of  the  leaves,  except  in  some  comparatively  rare 
and  exceptional  types,  has  also  been  much  the  same. 
Any  ordinary  observer  examining  a  collection  of  coal- 
formation  ferns  recognises  at  once  tlieir  kinship  to  the 
familiar  brackens  of  our  own  time.  Their  fructification 
is,  unfortunately,  rarely  preserved,  so  that  we  are  not 
able,  in  the  case  of  many  species,  to  speak  confidently  of 


Fio.  50. — Stems  of  CalamoJendron  and  tissues  magnified  (Nova  Scotia), 
a,  6,  Casts  of  axis  in  sandstone,  with  woody  envelope  (reduced). 
c,  d,  Woody  tissue  (highly  magnified). 

their  affinities  with  modern  forms  ;  but  the  knowledge  of 
this  subject  has  been  constantly  extending,  and  a  suffi- 
cient amount  of  information  has  been  obtained  to  enable 
us  to  say  something  as  to  their  probable  relationships. 
(Figs.  51  to  55.) 

The  families  into  which  modern  ferns  are  divided  are, 
it  must  be  confessed,  somewhat  artificial,  and  in  the  case 


1; 


i! 


I 


|i 


i 


II 


12G 


TUE  GEOLOGICAL  HISTORY  OF  PLANTS. 


of  fossil  ferns,  in  wliich  the  fructification  is  for  the  most 
part  wanting,  it  is  still  more  so,  depending  in  great  part 
on  the  form  and  venation  of  the  divisions  of  the  fronds. 


Fio.  51. — Group  of  coal-formation  ferns,  a,  Odontopteris  suhcuneata  (Bnu- 
bury).  B,  Neuropteria  cordata  (Brongniart).  c,  Alethopteris  lonc/dtica 
(Brongrniart).  d,  Dicti/opteris  obiiqud  I  Hunhury),  e,  Phyllopteris  an- 
tiqua  (Dawson),  magnified;  e>,  Natural  size,  f,  H'europteris  cyclopte- 
roidea  (Dawson). 

Of  about  eight  families  into  which  modern  ferns  are 
divided,  seven  are  found  in  a  fossil  state,  and  of  these, 
four  at  least,  the  Ci/aihacew,  the  OpMoglossecB,  the  Hy- 


THE  CARBONIFEROUS  FLORA. 


127 


FiQ.  b2.—Alethopteri8  grandis  (Dawson).    Middle  coal-formation  of  Nova 

Scotia. 


Fig.  bZ.—Cyclopteris  (Aneimites)  Acadica  CDawson),  a  tree-fern  of  the 
Lower  Carboniferous,  a,  Pinnules.  6,  Fragment  of  petiole,  c,  Re- 
maina  of  fertile  pinnules. 


It       I 
l!         1 


(1 


I 


: 


I 


128 


THE   GEOLOGICAL  HISTORY  OP  PLANTS. 


menophyllacecB,  and  the  Marattiaccw,  go  back  to  the  coal- 
formation.* 

Some  of  these  ferns  have  the  more  complex  kind  of 
spore-case,  with  a  jointed,  elastic  ring.     It  is  to  be  ob- 


Fio.  54. — Sphenopteria  latior,  Dawson.    Coal-formntion.    a,  Pinnule 
magnifled,  with  traces  of  fructiliuation. 

served,  however,  that  those  forms  which  have  a  simple 
spore-case,  either  netted  or  membranous,  and  without 
annulus,  are  most  common  in  the  Devonian  and  lowest 


Fio.  55. — Fructification  of  Paloeozoic  ferns,  a,  Thecre  of  Archceopteris 
(Erian).  6,  Theea  of  Setiftenbergia  (CarboniferQus).  c,  Thecffi  of 
Asterotheca  (Carboniferous). 

Carboniferous.     Some  of  the  forms  in  these  old  rocks  are 
somewhat  difficult  to  place  in  the  system.     Of  these,  the 

*  Mr.  R.  Kidston  has  recently  described  very  interesting  forms  of 
fern  fructification  from  the  coal-formation  of  Great  Britain,  and  much 
has  been  done  by  European  palseobotanists,  and  also  by  Lesquereux  and 
Fontaine  in  America. 


THE  CARBONIFER(>DS  FLORA. 


129 


Fio.   56. — Tree-ferns  of  the  Carboniferous,    a,  MegapTiijton  mnrfnificum, 
\  Dawson,  restored,     b,  Leaf-scar  of  the  same,  two  thirds  natural  size. 

V  B'    Row  of  leaf-sears,  reduced,     c,  I'uLvopterU  Ihrtii^  f^Q&xH  h&M  iiixi\x- 

ral  size,    d,  Jiilceopteris  Acadica^  scars  half  natural  size, 

18 


t  till   " 


•i^    ; 


130 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


allied  to  the  gingko-trce  of  China 


species  of  Archmopteris,  of  the  Upper  and  Middle  Erian, 
are  eminent  as  examples.  This  type,  however,  scarcely 
extends  as  high  as  the  coal-formation.*  Some  of  the 
tree-ferns  of  the  Carboniferous  present  very  remarkable 
features.  One  of  these,  of  the  genus  Megaphyton,  seems 
to  have  two  rows  of  great  leaves,  one  at  each  side  of  the 
stem,  which  was  probably  sustained  by  large  bundles  of 
aerial  roots  (Fig.  56). 

In  the  Carboniferous,  as  in  the  Erian,  there  are  leaves 
which  have  been  referred  to  ferns,  but  are  subject  to 
doubt,  as  possibly  belonging  to  broad-leaved  taxine  trees 

One  of  these,  repre- 
sented in  Fig.  57,  has  been 
found  in  the  coal-formation  of 
Nova  Scotia,  and  referred  to  the 
doubtful  genus  Nocggcrathia. 
Fontaine  has  proposed  for  simi- 
lar leaves  found  in  Virginia  the 
new  generic  name  Saportca. 

Ferns,  as  might  be  inferred 
from  their  great  age,  are  at  the 
present  time  dispersed  over  the 
whole  world  ;  but  their  head- 
qusirters,  and  the  regions  to 
wliich  tree-ferns  are  confined, 
are  the  more  moist  climates  of  the  tropics  and  of  the 
southern  hemisphere.  The  coal-swamps  of  the  northern 
hemisphere  seem  to  have  excelled  even  these  favoured 
regions  of  the  j)resent  world  as  a  paradise  for  ferns. 

I  have  already  stated  that  the  Carboniferous  consti- 
tutes the  headquarters  of  the  Coriaites  (Fig.  58),  of  which 
a  large  uumber  of  species  have  been  described,  both  in 

*  The  pretty  little  ferns  of  (.^  j  genus  Botryehium  (moonwort),  so 
common  in  American  and  European  woods,  seem  to  be  their  nearest  mod- 
ern allies. 


Fio.  57. — Noeggerathia  dispar 
(half  nutiirul  size). 


THE  CARBONIFEROUS  FLORA. 


131 


Europe  and  Arr/^rica.  We  sometimes,  though  rarely, 
find  their  stems  showing  structure.  In  this  case  we  have 
a  large  cellular  pith,  often  divided  by  horizontal  parti- 
tions into  flat  chambers,  and  constituting  the  objects 
which,  when  detached,  are  called  SternhergicB  (Fig.  G2). 
These  Sternbergia  j)iths,  however,  occur  in  true  coni- 
fers as  well,  as  they  do 
in  the  modern  world 
in  some  trees,  like  our 
common  butternut,  of 
higher  type  ;  and  I 
showed  many  years  ago 
that  the  Sternbergia 
type  may  be  detected 
in  the  young  twigs  of 
the  balsam -fir  {Abies 
balsamifera).  The  pith 
was  surrounded  by  a 
ring  of  scalariform  or 
barred  tissue,  often  of 
considerable  thickness, 
and  in  young  stems  so 
important  as  to  have 
suggested  lycopodia- 
ceous  aflBnities.  But  as 
the  stem  grew  in  size, 
a  regular  ring  of  woody 
wedges,  with  tissue  hav- 
ing rounded  or  hex- 
agonal pores  or  discs, 
like  those  of  pines,  was  developed.  Outside  this  was  a 
bark,  often  apparently  of  some  thickness.  This  struct- 
ure in  many  important  points  resembles  that  of  cycada, 
and  also  approajiis  to  the  structure  of  Sigillaria,  while 
in  its  more  higlily  ac,?1opcd  forms  it  approximates  to 
that  of  the  conifers. 


Fio.  58. —  Cf^rdaiku  ( Dor>/cordai(es), 
Grand'  Eury,  reduced. 


(1 


r!i''i 


i:  :;i  i' 


I' 


N 


ill 


n 


H 


132 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


On  the  stems  so  constructed  were  placed  long  and 
often  broad  many-nerved  leaves,  with  rows  of  stomata  or 
breathing-pores,  and  attached  by  somewhat  broad  bases 
to  the  stem  and  branches.  The  fruit  consisted  of  racemes, 
or  clusters  of  nutlets,  which  seem  to  have  been  provided 


Fio.  59. — Fruits  of  Cordaites  and  Taxine  Conifers  fcoal-forraation.  Nova 
Scotia.)  A,  Antholithei^  nqunmoswi  (two  thirds),  b,  A.  rliohaocurpi 
(two  thirds).  ]i>,  Curpel  restored,  o,  A.  (t/iinoKiw  (natural  size). 
I),  Trigonofarpum  inttrnwilinm.  e,  T.  JVonfrtjenit/iii.  k,  T.  avdla- 
niim.  o,  Jihabdocnrpxis  insiijnid,  reduced,  n,  AntholUhes  pijgma'us, 
I,  Cardiomrpum  fuitans.  k,  Cai'dincarpitm  hi»ectiim.  i.,  Sporangites 
papilluiay  lycopoiliuceous  macrosporoB  (natural  feize  and  raa;j;niflcd). 


THE  CARBONIFEROUS  FLORA. 


133 


M 


with  broad  lateral  wings  for  flotation  in  the  air,  or  in 
some  cases  with  a  pulpy  envelope,  which  flattens  into  a 
film.  There  seem  to  have  been  structures  of  both  these 
kinds,  though  in  the  state  of  preservation  of  these  curious 
seeds  it  is  extremely  difficult  to  distinguish  them.  In  the 
first  case  they  must  have  been  intended  for  dissemination 
by  the  wind,  like  the  seeds  of  spruces.  In  the  latter  case 
they  may  have  been  disseminated  like  the  fruits  of  taxine 
trees  by  the  agency  of  animals,  though  what  these  were 
it  would  be  difficult  to  guess.  These  trees  had  very  great 
reproductive  power,  since  they  produced  numerous  seeds, 
not  singly  or  a  few  together,  as  in  modern  yews,  but  in 
long  spikes  or  catkins  bearing  many  seeds  (Fig.  59). 

It  is  to  be  observed  that  the  Cordaites,  or  the  Cor- 
daitincB,  as  they  have  been  called,  as  a  family,*  constitute 
another  of  those  intermediate  groups  with  which  we  have 
already  become  familiar.  On  the  one  hand  they  approach 
closely  to  the  broader-leaved  yews  like  Gingko,  Phyllo- 
cladus,  and  Podocarpus,  and,  on  the  other  hand,  they 
have  affinities  with  Cycadaceae,  and  even  with  Sigillaria3. 
They  were  beautiful  and  symmetrical  trees,  adding  some- 
tiiing  to  the  variety  of  the  rather  monotonous  Palaeo- 
zoic forests.  They  contributed  also  somewhat  to  the  ac- 
cumulation of  coal.  I  have  found  that  some  thin  beds  are 
almost  entirely  composed  of  their  leaves,  and  the  tissues 
of  their  wood  are  not  infrequent  in  the  mineral  charcoal 
of  the  larger  coal-seams.  There  is  no  evidence  that  their 
root«  were  of  the  stigmaroid  type,  thoui^h  tlicy  evidently 
grew  in  the  same  swampy  flats  with  the  Sigillaria3  and 
Calami  tes. 

It  may,  perhaps,  be  well  to  say  here  tliat  I  believe 
there  was  a  considerably  wide  range  of  organisation  in  the 
CordaitinjE  as  well  as  in  the  Calamites  and  Sigillarire,  and 
that  it  will  eventually  be  found  that  there  were  three  lines 


W 


*  Englcr ;   Cordaitees  of  Renault. 


il 

il 


hi  ; 


I 


tit 
III 


I'l 


|: 


I 


134 


7HE  GEOLOGICAL  HISTORY  OF  PLANTS. 


of  connection  between  the  higher  cryptogams  and  the 
phaenogams,  one  leading  from  the  lycopods  by  the  Sigil- 
lariee,  another  leading  by  the  Cordaites,  and  the  third 
leading  from  the  E(jaisetums  by  the  Calami tes.  Still 
further  back  the  characters  afterward  separated  in  the 
club-mosses,  mare's-tails,  and  ferns,  were  united  in  the 
Rhizocarps,  or,  as  some  now,  but  I  think  somewhat  un- 
reasonably, prefer  to  call  them,  the  "  heterosporous  Fili- 
cina3."  In  the  more  modern  world,  all  the  connecting 
links  have  become  extinct  and  the  phaenogams  stand 
widely  separated  from  the  higher  cryptogams.  I  do  not 
make  these  remarks  in  a  Darwinian  sense,  but  merely  to 
state  what  appear  to  be  the  lines  of  natural  affinity  and 
the  links  wanting  to  give  unity  to  the  system  of  nature. 

Of  all  the  trees  of  the  modern  world,  none  are  perhaps 
so  widely  distributed  as  the  pines  and  their  allies.  On 
mountain-tops  and  within  the  Arctic  zone,  the  last  trees 
that  can  struggle  against  the  unfavourable  conditions  of 
existence  are  the  spruces  and  firs,  and  in  the  warm  and 
moist  islands  of  the  tropics  they  seem  equally  at  home 
with  the  tree-ferns  and  the  palms.  We  have  already  seen 
that  they  are  a  very  ancient  family,  and  in  the  sandstones 
of  the  coal-formation  their  great  truiiks  are  frequently 
found,  infiltrated  with  calcareous  or  silicious  matter,  and 
still  retaining  their  structure  in  the  greatest  perfection 
(Fig.  60).  So  far  as  we  know,  the  foliage  of  some  of  them 
which  constitutes  the  genera  Walchia  and  Araucarites  of 
some  authors  (Figs.  60,  63)  was  not  dissimilar  from  that 
of  modern  yews  and  spruces,  though  there  is  reason  to 
believe  that  some  others  had  broad,  fern-like  leaves  like 
those  of  the  gingko.  None  of  them,  so  far  as  yet  cer- 
tainly known,  were  cone-bearing  trees,  their  fruit  having 
probably  been  similar  to  that  of  the  yews  (Fig.  61). 
The  minute  structures  of  their  stems  are  nearer  to  those 
of  the  conifers  of  the  islands  of  the  southern  hemisphere 
than  to  that  of  those  in   our   northern  climes — a  cor- 


THE  CARBONIFEROUS  FLORA 


Fio.  fiO. — Coniferous  wood  and  t'orui>.'e  (Carbonil'orouH).  a,  Aravcarifes 
grdcilis^  reduced.  B,  Dadoxi/loii  Acndi'itium  (radinl),  90  dimiiH. ; 
B'  0^"'>Kcntiul),  90  dianiH. ;  b»,  cell  showiiij^  areolation,  250  diams. 
c,  Dalori/lon  materinrinm  (radinl),  90  diams. ;  c'  (tan<rcntiai),  90 
diaras. ;  c",  cell  showing  areolation,  250  diams.  u,  D<i(l'>x//lon  tinti- 
qiiiiiK  ^radial),  90  diams.;  u*  (tunguntiul),  90  diums. ;  u",  cell  showing 
areolation,  260  diuuis. 

•  ■ .         -    ■        u.. 


«  0*00,,*      «    «      ,,■ 

O  ■>       ■  5      0         J        J     3    0        «       > 


T^-7^ 


r 


i  i 


y  ;   \ 


II  p  i 


I 


136 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


relation,  no  doubt,  to  the  equable  climate  of  the  period. 
There  is  not  much  evidence  that  they  grew  with  the  Si- 
gillariae  in  the  true  coal-swamps,  though  some  specimens 
have  been  found  in  this  association.  It  is  more  likely 
that  they  were  in  the  main  inland  and  upland  trees,  and 

B    d 


Fig.  61. — Trigonocarpum  Hooheri,  Daw- 
son, from  "the  coal-measures  of  Cape 
Breton.    Probably  the  fruit  of  a  Tax- 
"'  ine  tree,    a,  Broken  specimen  magni- 

fied twice  natural  size,  b,  Section  magnified :  a,  tiie  testa ;  ft,  the  teg- 
men;  c,  the  nucleus;  d,  the  embryo,  c,  Portion  of  the  surface  of  the 
inner  coat  more  highly  magnified. 

',  ■■< 

that  in  consequence  they  are  mostly  known  to  us  by 
drifted  trunks  borne  by  river  inundations  into  the  seas 
and  estuaries. 

A  remarkable  fact  in  connection  with  them,  and  show- 
ing also  the  manner  in  which  the  most  durable  vegetable 
structures  may  perish  by  decay,  is  that,  like  the  Cordaites, 
they  had  large  piths  with  transverse  partitions,  a  struct- 


THE  CARBONIFEROUS  FLORA. 


137 


uro  which,  as  I  have  already  mentioned,  appears  on  a 
minute  scale  in  the  twigs  of  the  fir-tree,  and  that  some- 
times casts  of  these  piths  in  sandstone  appear  in  a  separate 
form,  constituting  what  have  heen  named  Sternbcrgim  or 
Artisiw.  As  Renault  well  remarks  with  reference  to 
Cordaites,  the  existence  of  this  chambered  form  of  pith 
implies  rai)id  elongation  of  the  stem,  so  that  the  Cordaites 
and  conifers  of  the  coal-formation  were  probabl}'  quickly 
growing  trees  (Fig.  62). 

The  same  general  statements  may  be  made  as  to  the 
coal-vegetation  as  in  relation  to  that  of  the  Erian.     In 


'*  *WWW„„ 


't»lniftrilf'^ff}ftfttl' 


iilL.i; 

i'Mr' 

';iiiHi",'i 

,l;iJM|i 

|liill!|i,l| 

a 


a 


CL 


Fio.  62. — Sternhergia  pith  of  Dadoxylon.  a,  Specimen  (natural  size), 
sliowinj;  renmins  of  wood  at  a,  <t.  b,  Junction  of  wood  and  pith,  inag- 
nifled.  c,  Culls  of  the  wood  of  do.,  a,  «;  6,  medullary  ray;  c,  arco- 
lation. 


the  coal  period  we  have  found  none  of  the  higher  ex- 
ogens,  and  there  are  only  obscure  and  uncertain  indica- 
tions of  the  presence  of  endogens,  which  we  may  reserve 
for  a  future  chapter  ;  but  gymnosperms  abound  and  are 
highly  characteristic.  On  the  other  hand,  wo  have  no 
mosses  or  lichens,  and  very  few  Algse,  but  a  great  num- 
ber of  ferns  and  Lycopodiaceae  or  club-mosses  (Fig.  03). 
Thus,  the  coal-formation  period  is  botunically  a  meeting- 
place  of  the  lower  phjBnogams  and  the  higher  cryptogams, 
and  presents  many  forms  which,  when  imperfectly  known, 
have  puzzled  botanists  in  regard  to  their  position  in  one 
or  other  series.     In  the  present  world,  the  flora  most  akin 


138 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


1;    :: 

ill?  M 


Ml 


H 


II ' 


to  that  of  the  coal  period  is  that  of  warm,  temperate  re- 
gions in  the  southern  hemisphere.  It  is  not  properly  a 
tropical  flora,  nor  is  it  the  flora  of  a  cold  region,  but 
rather  indicative  of  a  moist  and  equable  climate.     Still, 


Fio.  63. —  Walchia  imbricatula,  S.  N.,  Permian,  Prince  Edward  Island. 

we  must  bear  in  mind  that  we  may  often  be  mistaken  in 
reasoning  as  to  the  temperature  required  by  extinct 
species  of  plants,  differing  from  .hose  now  in  existence. 
Further,  we  must  not  assume  that  the  climatal  conditions 
of  the  northern  hemisphere  were  in  the  coal  period  at  all 
similar  to  those  which  now  prevail.  As  Sir  Charles  Lyell 
has  shown,  a  less  amount  of  land  in  the  higher  latitudes 
would  greatly  modify  climates,  and  there  is  every  reason 
to  believe  that  in  the  coal  period  there  was  less  land  than 
now.  Further,  it  has  been  shown  by  Tyndall  that  a  very 
small  additional  amount  of  carbonic  acid  in  the  atmos- 
phere would,  by  obstructing  the  radiation  of  heat  from 
the  earth,  produce  almost  the  effect  of  a  glass  roof  or  con- 
servatory, extending  over  the  whole  world.  Again,  there 
is  much  in  the  structure  of  the  leaves  of  the  coal-plants, 
as  well  as  in  the  vast  amount  of  carbon  which  they  ac- 
cumulated in  the  form  of  coal,  and  the  characteristics  of 
the  animal  life  of  the  period,  to  indicate,  on  independent 


"!^ 


THE  CARBONIFEROUS  FLORA, 


139 


grounds,  that  the  carboniferous  atmosphere  diflfered  from 
that  of  the  present  world  in  this  way,  or  in  tlie  presence 
of  more  carbonic  acid — a  substance  now  existing  in  the 
very  minute  proportion  of  one  thousandth  of  the  whole — 
a  quantity  adapted  to  the  present  requirements  of  vege- 
table and  animal  life,  but  probably  not  to  those  of  the 
coal  period. 

Thus,  if  we  inquire  as  to  any  analogous  distribution  of 
plants  in  the  modern  world,  we  find  this  only  in  the  warm- 
er insular  climates  of  the  southern  hemisphere,  where 
ferns,  lycopods,  and  pines  appear  under  forms  some- 
what akin  to  those  of  the  Carboniferous,  but  mixed  with 
other  types,  some  of  which  are  modern,  others  allied  to 
those  of  the  next  succeeding  geological  ages  of  the  Meso- 
zoic  and  Tertiary ;  and  under  these  periods  it  will  be 
more  convenient  to  make  comparisons. 

The  readers  of  recent  English  pojiular  works  on  geol- 
ogy will  have  observed  the  statement  reiterated  that  a 
large  proportion  of  the  material  of  the  great  beds  of  bi- 
tuminous coal  is  composed  of  the  spore-cases  of  lycopo- 
diaceous  plants — a  statement  quite  contrary  to  that  re- 
sulting from  my  microscopical  examinations  of  the  coal 
of  more  than  eighty  coal-beds  in  Nova  Scotia  and  Cape 
Breton,  as  stated  in  "Acadian  Geology"  (page  463),  and 
more  fully  in  my  memoir  of  1858  on  the  '*  Structures  in 
Coal,"  *  and  that  of  1866,  on  the  "  Conditions  of  Ac- 
cumulation of  Coal."f  The  reason  of  this  mistake  is, 
that  an  eminent  nglish  naturalist,  happening  to  find  in 
certain  specimens  of  English  coal  a  great  quantity  of  re- 
mains of  spores  and  spore-cases,  though  even  in  his  speci- 
mens they  constitute  only  a  small  portion  of  the  mass, 
and  being  apparently  unacquainted  with  what  others  had 
done  in  this  field,  wrote  a  popular  article  for  the  **  Con- 
temporary Review,"  in  which  he  extended  an  isolated  and 


*  "  Journal  of  the  Geological  Society,"  vol.  xv.        f  Ibid.,  vol.  xxii. 


H 


I  I 


I    I  i 


140 


THE  GEOLOGICAL   HISTORY  OF   PLANTS. 


exceptional  fact  to  all  coals,  and  plnccd  this  supposed 
origin  of  coal  in  a  light  so  brilliant  and  attractive  that  he 
has  been  followed  by  many  recent  writers.  The  fact  is, 
as  stated  in  "  Acadian  Geology,"  that  trunks  of  SifjillaricB 
and  similar  trees  constitute  a  great  part  of  the  denser 
portion  of  the  coal,  and  that  the  cortical  tissues  of  these 
rather  than  the  wood  remain  as  coal.  But  cortical  or 
epidermal  tissues  in  general,  whether  those  of  spore-cases 
or  other  parts  of  plants,  are  those  which  from  their  re- 
sistance to  water-soakage  and  to  decay,  and  from  their 
highly  carbonaceous  character,  are  best  suited  to  the  pro- 
duction of  coal.  In  point  of  fact,  spore-cases,  though 
often  abundantly  present,  constitute  only  an  infinitesimal 
part  of  th "  matter  of  the  great  coal-beds.  In  an  article 
in  **  The  American  Journal  of  Science,"  which  appeared 
shortly  after  that  above  referred  to,  I  endeavoured  to  cor- 
rect this  error,  though  apparently  without  effect  in  so  far 
as  the  majority  of  British  geological  writers  are  con- 
cerned. From  this  article  I  have  taken  with  little  change 
the  following  passages,  as  it  is  of  importance  in  theoretical 
geology  that  such  mistakes,  involving  as  they  do  the 
"whole  theory  of  coal  accumulation,  should  not  continue 
to  pass  current.  The  early  part  of  the  paper  is  occupied 
with  facts  as  to  the  occurrence  of  spores  and  spore-cases  as 
partial  ingredients  in  coal.  Its  conclusions  are  as  follows  : 
.'  It  is  not  improbable  that  sporangites,  or  bodies  re- 
sembling them,  may  be  found  in  most  coals ;  but  it 
is  most  likely  that  their  occurrence  is  accidental  rather 
than  essential  to  coal  accumulation,  and  that  they  are 
more  likely  to  have  been  abundant  in  shales  and  cannel 
coals,  deposited  in  ponds  or  in  shallow  waters  in  the  vi- 
cinity of  lycopodiaceous  forests,  than  in  the  swampy 
or  peaty  deposits  which  constitute  the  ordinary  coals. 
It  is  to  be  observed,  however,  that  the  conspicuous  ap- 
pearance which  these  bodies,  and  also  the  strips  and 
fragments  of  epidermal  tissue,  which  resemble  them  in 


THE  CARBONIFEROUS  FLORA. 


141 


texture,  present  in  slices  of  coal,  may  incline  an  observer, 
not  having  large  experience  in  the  examination  of  coals, 
to  overrate  tiieir  importance  ;  and  this  I  think  has  been 
done  by  most  niicroscopists,  especially  those  who  have 
confined  their  attention  to  slices  prepared  by  the  lapidary. 
One  must  also  bear  in  mind  the  danger  arising  from  mis- 
taking concretionary  accumulations  of  bituminous  matter 
for  sporangia.  Tn  sections  of  the  bituminous  shales  ac- 
companying the  Devonian  coal  above  mentioned,  there 
are  many  rounded  yellow  spots,  which  on  examination 
prove  to  be  the  spaces  in  the  epidermis  of  PsilophijtGn 
through  which  the  vessels  passing  to  the  leaves  were 
emitted.  To  these  considerations  I  would  add  the  fol- 
lowing, condensed  from  the  paper  above  referred  to 
(p.  139),  in  which  the  whole  question  of  the  origin  of 
coal  is  fully  discussed  :* 

1.  The  mineral  charcoal  or  *  mother  coal'  is  obviously 
woody  tissue  and  fibres  of  bark,  the  structure  of  the  va- 
rieties of  which,  and  the  plants  to  which  it  probably  be- 
longs, I  have  discussed  in  the  paper  above  mentioned. 

2.  The  coarser  layers  of  coal  show  under  the  micro- 
scope a  confused  mass  of  fragments  of  vegetable  matter 
belonging  to  various  descrij^tions  of  plants,  and  includ- 
ing, but  not  usually  in  large  quantities,  sporangites. 

3.  The  more  brilliant  layers  of  the  coal  are  seen, 
when  separated  by  thin  laminas  of  clay,  to  have  on  their 
surfaces  the  markings  of  Sigillarim  and  other  trees,  of 
which  they  evidently  represent  flattened  specimens,  or 
rather  the  bark  of  such  specimens.  Under  the  micro- 
scope, when  their  structures  are  preserved,  these  layers 
show  cortical  tissues  more  abundantly  than  any  otliers. 

4.  Some  thin  layers  of  coal  consist  mainly  of  flat- 
tened layers  of  leaves  of  Cordaitcs  or  Pyclmophylluni. 

5.  The    Stigmaria    underclays  and  the   stumps  of 


*  See  also  "Acadian  Geology,"  2d  ed.,  pp.  138,  461,  49.3. 
14 


M 


142 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


Siyillaria  in  the  coal-roofs  equally  testify  to  the  accu- 
mulation of  coal  by  the  growtli  of  successive  forests,  more 
especially  of  Sigillarim.  There  is,  on  the  other  hand,  no 
necessary  connection  of  sporangite-beds  with  Stigniarian 
soils.  Such  beds  are  more  likely  to  bo  accumulated  in 
water,  and  consequently  to  constitute  bituminous  shales 
and  canncls. 

6.  Lepidodendron  and  its  allies,  to  which  the  spore- 
cases  in  question  appear  to  belong,  are  evidently  much 
less  important  to  coal  accumulation  than  Sigillaria,  which 
cannot  be  affirmed  to  have  produced  spore-cases  similar 
to  those  in  question,  even  though  the  observation  of 
Goldenberg  as  to  their  fruit  can  be  relied  on  ;  the  ac- 
curacy of  which,  however,  I  am  inclined  to  doubt. 

On  the  whole,  then,  while  giving  due  credit  to  those 
who  have  advocated  the  spore-theory  of  coal,  for  directing 
attention  to  this  curious  and  no  doubt  important  constit- 
uent of  mineral  fuel,  and  admitting  that  I  may  possibly 
have  given  too  little  attention  to  it,  I  must  maintain  that 
sporangite-beds  are  exceptional  among  coals,  and  that 
cortical  and  woody  matters  are  the  most  abundant  ingre- 
dients in  all  the  ordinary  kinds ;  and  to  this  I  cannot 
think  that  the  coals  of  England  constitute  an  exception. 

It  is  to  be  observed,  in  conclusion,  that  the  spore- 
cases  of  plants,  in  their  indestructibility  and  richly  car- 
bonaceous character,  only  partake  of  qualities  common  to 
most  suberous  and  epidermal  matters,  as  I  have  explained 
in  the  publications  already  referred  to.  Such  epidermal 
and  cortical  substances  are  extremely  rich  in  carbon  and 
hydrogen,  in  this  resembling  bituminous  coal.  They  are 
also  very  little  liable  to  decay,  and  they  resist  more  than 
other  vegetable  matters  aqueous  infiltration — properties 
which  have  caused  them  to  remain  unchanged,  and  to 
continue  free  from  mineral  additions  more  than  other 
vegetable  tissues.  These  qualities  are  well  seen  in  the 
bark  of  our  American  white  birch.     It  is  no  wonder  that 


THE  CARBONIFEROUS  FLORA. 


143 


materials  of  tins  kind  should  constitute  considerable 
portions  of  such  vegetable  accumulations  as  the  beds  of 
coal,  and  that  when  present  in  large  proportion  they 
should  afford  richly  bituminous  beds.  All  this  agrees 
with  the  fact,  api)arent  on  examination  of  the  common 
coal,  that  the  greater  number  of  its  purest  layers  consist 
of  the  flattened  bark  of  Sigillarim  and  similar  trees,  just 
as  any  single  flattened  trunk  embedded  in  shale  becomes 
a  layer  of  pure  coal.  It  also  agrees  with  the  fact  that 
other  layers  of  coal,  and  also  the  cannels  and  earthy 
bitumens,  appear  under  the  microscope  to  consist  of 
finely  comminuted  particles,  principally  of  epidermal  tis- 
sues, not  only  from  the  fruits  and  spore-cases  of  plants, 
but  also  from  their  loaves  and  stems.  These  considera- 
tions impress  us,  just  as  much  as  the  abundance  of  spore- 
cases,  with  the  immense  amount  of  the  vegetable  matter 
which  has  perished  during  the  accumulation  of  coal,  in 
comparison  with  that  which  has  been  preserved. 

I  am  indebted  to  Dr.  T.  Sterry  Hunt  for  the  fol- 
lowing very  valuable  information,  which  at  once  places 
in  a  clear  and  precise  light  the  chemical  relations  of 
epidermal  tissue  and  spores  with  coal.  Dr.  Hunt  says  : 
**The  outer  bark  of  the  cork-tree,  and  the  cuticle  of 
many  if  not  all  other  plants,  consists  of  a  highly  car- 
bonaceous matter,  to  which  the  name  of  suherin  has  been 
given.  The  spores  of  Lycopodium  also  approach  to  this 
substance  in  composition,  as  will  be  seen  by  the  follow- 
ing, one  of  two  analyses  by  Duconi,*  along  with  which 
I  give  the  theoretical  composition  of  pure  cellulose  or 
woody  fibre,  according  to  Payen  and  Mitscherlich,  and 
an  analysis  of  the  suherin  of  cork,  from  Quercus  suheVy 
from  which  the  ash  and  2*5  per  cent  of  cellulose  have 
been  deducted,  f 


*  Liebig  and  Kopp,  "  Jabresbuch,"  184'7-'48. 
f  Gmclin,  "  Handbook,"  xv,,  146. 


144 


THE  GEOLOGICAL  HISTORY  0?'  PLANTf. 


■5    3 


• 

Celluloso. 

44-44 
617 

49-39 
100-00 

Cork. 

Lycopodium. 

Carbon 

65  •  73 
8  •  33 

1-no 

24-44 

64  -  80 

IIvdr<)fi;cn 

8  73 

Nitrogen 

6- 18 

Oxygen 

20-29 

Total 

100-00 

100-00 

"This  difference  is  not  less  striking  when  we  reduce 
the  above  centesimal  analyses  to  correspond  with  the 
formula  of  cellulose,  0241120020,  and  represent  cork  and 
Lycopodium  as  containing  twenty-four  equivalents  of 
carbon.  For  comparison  I  give  the  composition  of  speci- 
mens of  peat,  brown  coal,  lignite,  and  bituminous  coal  :* 

Cellulose CaJI.joOao 

Cork (!.«H,„V>«i^ 

Lyeopodiuni ('a4lIiBi'uN0&i'\j 

Peat  (Vaux) Ca^IIwVVOio 

Brown  coal  (Sehrothcr) C24I1i4|',tO,oi''()  , 

Lignite  (Vaux) CaiHui'^irOniV 

I3i*uminous  coal  (Repnault) CaillioOai'o 

**It  will  be  seen  from  tliis  comparison  that,  in  ulti- 
mate composition,  cork  and  Lycopodium  are  nearer  to 
lignite  than  to  woody  fibre,  and  may  be  converted  into 
coal  with  far  loss  loss  of  carbon  and  hydrogen  than  the 
latter.  They  in  fact  ajjproach  closer  in  composition  to 
resins  and  fats  than  to  wood,  and,  moreover,  like  tlioso 
substances  repel  water,  with  which  they  are  not  easily 
moistened,  and  thus  ai  ~  able  to  resist  those  atmospheric 
influences  which  effect  tlie  decay  of  woody  tissue." 

I  would  add  to  this  only  one  further  consideration. 
The  nitrogen  present  in  the  Lycopodium  s{)()res,  no  doubt, 
belongs  to  the  protoplasm  contained  in  tliem,  a  substance 
which  would  soon  perish  by  decay  ;  and  subtracting  this, 
the  cell-walls  of  the  spores  and  the  walls  of  the  sporc- 

♦  "  Canadian  Naturalist,"  vi.,  253. 


TUE  CARBONIFEIIOUS  FLORA. 


145 


cases  would  be  most  suitable  material  for  the  production 
of  bituminous  coal.  But  this  suitableness  they  share  with 
the  epidermal  tissue  of  the  scales  of  strobiles,  and  of  the 
stems  and  leaves  of  ferns  and  lycopods,  and,  above  all, 
with  the  thick,  corky  envelope  of  the  stems  of  Siyillarim 
and  similar  trees,  which,  as  I  have  elsewhere  shown,* 
from  its  condition  in  the  prostrate  and  erect  trunks  con- 
tained in  the  beds  associated  with  coal,  must  have  been 
highly  carbonaceous  and  extremely  enduring  and  im- 
permeable to  water.  In  short,  if,  instead  of  **  spore-cases," 
we  read  **  epidermal  tissues  in  general,  including  spore- 
cases,"  all  that  has  been  affirmed  regarding  the  latter  will 
be  strictly  and  literally  true,  and  in  accordance  with  the 
chemical  composition,  microscopical  characters,  and  mode 
of  occurrence  of  coal.  It  will  also  be  in  accordance  with 
the  following  statement,  from  my  paper  on  the  "Struct- 
ures in  Coal,"  published  in  1859  : 

"A  single  trunk  of  Sigillaria  in  an  erect  forest  pre- 
sents an  epitome  of  a  coal-seam.  Its  roots  represent  the 
Stigmaria  underclay  ;  its  bark  the  compact  coal ;  its 
woody  axis  the  mineral  charcoal  ;  its  fallen  leaves  (and 
fruits),  with  remains  of  herbaceous  plants  growing  in  its 
shade,  mixed  with  a  little  oarthy  matter,  the  layers  of 
coarse  coal.  The  condition  of  the  durable  outer  bark  of 
erect  trees  concurs  with  the  chemical  theory  of  coal,  in 
showing  the  especial  suitableness  of  this  kind  of  tissue  for 
the  production  of  the  purer  compact  coals.  It  is  also 
probable  that  the  comparative  impermeability  of  the  bark 
to  mineral  infiltration  is  of  importance  in  this  respect, 
enabling  this  material  to  remain  unaffected  by  causes 
which  have  filled  those  layers,  consisting  of  herbaceous 
materials  and  decayed  wood,  with  pyrites  and  other  min- 
eral substances." 


*  "  Vegetable  Rtructiires  in  Coal,"  "  Journal  of  Geological  Society," 
,  026.     "  Conditions  of  Accuroulation  of  Coal,"  ibid.^  xxii.,  96.    "  Aca- 


XV, 


dian  Geology,"  197,  404. 


I! 


!i  I 


I  \ 


i:  ! 


i   ! 


I  .'I 


i'l  Y 
111'' 


146 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


We  need  not  go  far  in  search  of  the  uses  of  the  coal 
vegetation,  when  we  consider  the  fact  that  the  greatest 
civilised  nations  are  dependent  on  it  for  their  fuel.  With- 
out the  coal  of  the  Carboniferous  period  and  the  iron -ore 
which  is  one  of  the  secondary  consequences  of  coal  ac- 
cumulation, just  as  bog-ores  of  iron  occur  in  the  subsoils 
of  modern  peats,  it  would  have  been  impossible  either  to 
sustain  great  nations  in  comfort  in  the  colder  climates  of 
the  northern  hemisphere  or  to  carry  on  our  arts  and 
manufactures.  The  coal-formation  yields  to  Great  Brit- 
ian  alone  about  one  hundred  and  sixty  million  tons  of 
coal  annually,  and  the  miners  of  the  United  States  ex- 
tract mainly  from  the  Fame  formation  nearly  a  hundred 
million  tons,  while  the  British  colonies  and  dependen- 
cies produce  about  five  million  tons  ;  and  it  is  a  re- 
markable fact  that  it  is  to  the  English  race  that  the 
greatest  supply  of  this  buried  power  and  heat  and  li^ht 
has  been  given. 

The  grea  forests  of  the  coal  period,  while  purifying 
the  atmosphere  of  its  excess  of  unwholesome  carbonic 
acid,  were  storing  up  the  light  and  heat  of  Palaeozoic 
summers  in  a  form  in  which  they  could  be  recovered  in  our 
human  age,  so  that,  independently  of  their  uses  to  the 
animals  which  were  their  contemporaries,  they  are  indis- 
pensable to  the  existence  of  civilised  man. 

Nor  can  we  hope  soon  to  be  able  to  dispense  with  the 
services  of  this  accumulated  store  of  fuel.  The  forests 
oi  to-day  are  altogether  insufficient  for  the  supply  of  our 
wants,  and  though  we  are  beginning  to  apply  water-power 
to  the  production  of  electricity,  and  though  some  promis- 
ing plans  have  been  devised  for  the  utilisation  of  the 
direct  heat  and  light  of  the  sun,  we  are  still  quite  as  de- 
pendent as  any  of  our  predecessors  on  what  has  been  done 
for  us  in  the  Palaeozoic  age. 

In  the  pr'""'ous  pages  I  have  said  little  respecting  the 
physical  gr. ^raphy  of  the  Carboniferous  age  ;  but,  as  may 


:n! 


H 


THE  CARBONIFEROUS  FLORA. 


147 


m 


be  inferred  from  the  vegetation,  this  in  the  northern 
hemisphere  presented  a  greater  expanse  of  swampy  flats 
little  elevated  above  the  sea  than  we  find  in  any  other  pe- 
riod. As  to  the  southern  hemisphere,  less  is  known,  but 
the  conditions  of  vegetation  would  seem  to  have  been  es- 
sentially the  same. 

Taking  the  southern  hemisphere  as  a  whole,  I  have 
not  seen  any  evidence  of  a  Lower  Devonian  or  Upper  Si- 
lurian flora ;  but  in  South  Africa  and  Australia  there  are 
remains  of  Upper  Devonian  or  Lower  Carboniferous 
plants.  These  were  succeeded  by  a  remarkable  Upper 
Carboniferous  or  Permian  group,  which  spread  itself  all 
over  India,  Australia,  and  South  Africa,*  and  contains 
some  forms  (Vertcbraria,  Phyllotheca,  Glossoplcris,  &c.) 
not  found  in  rocks  of  similar  age  in  the  northern  hemi- 
sphere, so  that,  if  the  age  of  these  bods  has  been  correctly 
determined,  the  southern  hemis})liere  was  in  advance  in 
relation  to  some  genera  of  plants.  This,  however,  is  to 
be  expected  when  we  consider  that  the  Triassic  and  Ju- 
rassic flora  of  the  north  contains  or  consists  of  intruders 
from  more  southern  sites.  These  beds  are  succeeded  in 
India  by  others  holding  cycads,  &c.,  of  Upper  Jurassic 
or  Lower  Cretaceous  types  (Rajmahal  and  Jabalpur 
groups). 

Blanford  has  shown  that  there  is  a  very  great  similar- 
ity in  this  series  all  over  the  Australian  and  I'ldian  re- 
gion, f  Ilartt  and  Darby  have  in  like  manner  distin- 
guished Devonian  and  Carboniferous  forms  in  Brazil  akin 
to  those  of  the  northern  hemisphere.  Thus  the  southern 
hemisphere  would  seem  to  have  kept  pace  with  the  north- 
ern, and  according  to  Blanford  there  is  evidence  there  of 
cold  conditions  in  the  Permian,  separating  the  Palceozoic 


i."- 


*  Wyley,  "Journal  Geol.  Society,"  vol.  xxiii.,  p.  1'72;  Daintree,  ibid., 
vol.  xxviii. ;  also  Clarke  and  McCoy. 

f  "  Journal  Geol.  Society,"  vol.  xxxL 


!i|! 


i' 


148 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


flora  from  that  of  the  Mesozoic,  in  the  same  manner  that 
Ramsay  has  supposed  a  similar  period  of  cold  to  have  done 
north  of  the  equator.  This  would  imply  a  very  great 
change  of  climate,  since  we  have  evidence  of  the  exten- 
sion of  the  Lower  Carboniferous  flora  at  least  as  far 
north  as  Spitzbergen.  The  upper  coal-formation  we 
cannot,  however,  trace  nearly  so  far  north  ;  so  that  a 
gradual  refrigeration  may  have  been  going  on  before 
the  Permian.  Thus  in  both  hemispheres  there  was  a 
general  similarity  in  the  later  Palaeozoic  flora,  and  per- 
haps similar  conditions  leading  to  its  extinction  and  to 
its  replacement  by  that  to  be  described  in  the  next 
chapter.  - 


NOTES  TO  CHAPTER  IV. 


\'-i  i< 


i  1. 


I.  Characters  and  Classification  of  Palaeozoic  Plants. 

In  the  space  available  in  tV-  work  it  would  be  impossible  to 
enter  fully  into  the  classifleation  L  Palaeozoic  plants;  but  it  may  be 
well  to  notice  s'^me  important  points  for  the  guidance  of  those  who 
may  desire  to  collect  specimens;  more  especially  as  much  uncer- 
tainty exists  as  to  affinities  and  very  contradictory  statements  are 
made.  The  statements  below  may  be  regarded  as  the  results  of 
actual  observation  and  of  the  study  of  specimens  in  situ  in  the  rocks, 
as  well  as  in  the  cabinet  and  under  the  microscope. 

Gymnosperme^. 

Family  Conifer.e;  Genua  Dadoxylon,  Endlicher;   Araucarites, 
Goeppert ;  Araucarioxylon,  Kraus. 

The  trunks  of  this  genus  occur  from  the  Middle  Devonian  to  the 
Permian  inclusive,  as  drift-logs  calcified,  silicified,  or  pyritised.  The 
only  foliage  associated  with  them  is  of  the  type  of  Walchia  and 
Araucarites — viz.,  slender  branches  with  numerous  small  spiral  acicu- 
lar  leaves.  Two  of  the  coal-formation  species,  D.  materianim  and 
another,  had  foliage  of  this  type.  That  of  the  others  is  unknown. 
They  are  all  distinct  from  the  wood  of  Cordaites,  for  which  see  under 
that  genus. 


THE  CARBONIFEROUS  FLORA. 


149 


The  following  are  North  American  species: 

Trunks. 

Dadoxylon  Ouangondianum,  Dn  .  .M.  Erian Report,  1871.* 

n.IIalti,  Dn "       

D.  Neivherryi,  Dn "       " 


Report,  1882. 
Acadian  Geol- 
ogy. 


1).  Clarkii,  Dn.  (Cordicoxylon  ?) . . .        "       

D.  Acadianum,  Dn Coal  -  formation 

;  ^  and  millstone 

grit. 
D.  Maleriarum,  Dn Do.    and    Pernio-  " 

Carb. 
Z>.  (Palajoxylon)  antiquius,  Dn  . .  .L.  Carboniferous.  " 

D.  annxilatum,  Dn Coal-formation.  " 

Orrnoxylon  Erianum,  Dn Erian Report,  1871. 

Foliage. 

Arancarites  gracilis,  Dn N.  Coal-formation  " 

and  Permian. 


Walchia  robusfa,  Dn.. 
W.  imbricatula,  Dn.. . 


Permian. 


Report    on 
Prince    Ed- 
ward Island. 


All  of  the  above  can  be  vouclied  for  as  good  species  ba«!ed  xipon 
microscopic  examination  of  a  very  large  number  of  trunks  from  dif- 
ferent parts  of  North  America.  The  three  Erian  species  of  Dadoxylon 
and  D.  antiquius  from  the  Lower  Carlxmiferous  have  two  or  more 
rows  of  cells  in  the  medullary  rays.  The  last  named  has  several 
rows,  and  is  a  true  Palo'oxylon  allied  to  D.  Withami  of  Great 
Britain.  1).  maferiarium  is  specially  characteristic  of  the  upper 
coal-formation  and  Permian,  and  to  it  must  belong  one  or  both  of 
the  species  of  foliage  indicated  above.  D.  Clarkii  has  very  short, 
simple  medullary  rays  of  only  a  few  cells  superimposed,  and  has  an 
inner  cylinder  of  sculariform  vessels,  approaching  in  these  jioints  to 
Cordaites.  Orrnoxylon  has  a  very  peculiar  articulated  pith  and 
simple  medullary  rays. 

Witham  in  1838  described  several  Carboniferous  species  of  pine- 
wood,  under  the  generic  name  Pinites,  separating  under  the  name 
Pitus  species  which  appeared  to  have  the  discs  on  the  cell-walls 


*  "  Geological  Survey  of  Canada :  Fossil  Plants  of  Erian  and  Upper 
Silurian  Formations,"  by  J.  W.  DaNvson. 


IT 


w^ 


150 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


i;  •*- 


!  8i^ 


separate  and  in  transverse  lines.  Witham's  name  was  changed  by 
Goeppert  to  Araucarites,  to  indicate  the  similarity  of  these  woods  to 
Araucaria,  Pinites  being  reserved  for  trees  more  closely  allied  to  the 
ordinary  pines.  Endlicher,  restricting  Araucarites  to  foliage,  etc., 
of  Araiicaria-like  trees,  gave  the  name  Dadoxylon  to  the  wood ;  and 
this,  through  Unger's  "  Genera  and  Species,"  has  gained  somewhat 
general  acceptance.  Endlicher  also  gave  the  name  Pissadendron  to 
the  species  which  Witham  had  called  Pitua;  but  Brongniart  pro- 
posed the  name  Palmoxylon  to  include  all  the  species  with  thick 
and  complex  medullary  rays,  whatever  the  arrangement  of  the  discs. 
In  Schimper's  new  work  Kraus  substitutes  Araucarioxylon  for  End- 
licher's  Dadoxylon,  and  includes  under  Pissadendron  all  the  species 
placed  by  Brongniart  in  Palceoxylon. 

To  understand  all  this  confusion,  it  may  bo  observed  that  the 
characters  available  in  the  determination  of  Palaeozoic  coniferous 
wood  are  chiefly  the  form  and  arrangement  of  the  wood-cells,  the 
character  of  the  bordered  pores  or  discs  of  their  walls,  and  the  form 
and  composition  of  the  medullary  rays. 

The  character  on  which  Witham  separated  his  genus  Pitus  from 
Pinites  is,  as  I  have  ascertained  by  examination  of  slices  of  one  of 
his  original  specimens  kindly  presented  to  me  by  Mr.  Sanderson,  of 
Edinburgh,  dependent  on  state  of  preservation,  the  imperfectly  pre- 
served discs  or  areolations  of  the  walls  of  the  fibre  presenting  the 
appearance  of  separate  and  distinct  circles,  while  in  other  parts  of 
the  same  specimens  these  discs  are  seen  to  be  contiguous  and  to  as- 
sume hexagonal  forms,  so  that  in  this  respect  they  do  not  really 
differ  from  the  ordinary  species  of  Dadoxylon.  The  true  character 
for  subdividing  those  species  which  are  especially  characteristic  of 
the  Carboniferous,  is  the  composite  structure  of  the  medullary  rays, 
which  are  thick  and  composed  of  several  radial  piles  of  cells  placed 
side  by  side.  This  was  the  character  employed  by  Brongniart  in 
separating  the  genus  Palo'oxylon,  though  he  might  with  convenience 
have  retained  Witham's  name,  merely  transferring  to  the  genus  the 
species  of  Witham's  Ignites  which  have  complex  medullary  rays. 
The  Erian  rocks  present  the  greatest  variety  of  types,  and  Palceoxylon 
is  especially  characteristic  of  the  Lower  Carboniferous,  while  species 
of  Dadoxylon  with  two  rows  of  bordered  pores  and  simple  medullary 
rays  are  especially  plentiful  in  the  upper  coal-formation  and  Permo- 
Carboniferous. 

The  following  table  will  clearly  show  the  distinctive  characters 
and  relations  of  the  genera  in  question,  as  held  by  the  several  authors 
above  referred  to :  /         .  ,  .  *        , 


■■■■  ■•! 


THE  CARBONIFEROUS  FLORA. 


151 


Wood  of  Palaozoic  Conifers. 


Woody  fibres. 

Medullary  rayiuid  pitb. 

Generic  ntmei. 

Geological  age. 

No  discs. 

One  or  two  series 
of  cells. 

Aporoxylon,  Unger. 

Devonian 
(Erian). 

Complex,  or  of  two 
or  more  series  of 
cells. 

Pith  Sternbergian. 

r  PituK,  Witham. 

PalcEoxylon,  Brongni- 
-(     art. 

Pinsndendron,  End- 
t    licher. 

Middle       and 
Lower     Car- 
boniferous 
and  Devo- 
nian. 

Discs  in  one  se- 
ries   contigu- 
ous, or  in  sev- 
eral       series 

Simple,  or  of  one 

row  of  cells. 
Pith  Sternbergian. 

Araucaritea,  Goeppert 
Dadoxylon,  Endhcner. 
Arancarioxylon, 
.    Schimper. 

Ormoxylon*  Dn. 

Upper  CartK>- 
niferous  and 
Permian. 

spirally      ar- 
ranged. 

Pith   in    spherical 
chambers. 

Devonian. 

Medullary    sheath 
sealariform. 

Medullary        rays 
frequeut,  simple, 
short. 

Dadoxylon  (Cordaoxy- 
lon),+  Dn. 

Devonian. 

♦  Type  O.  Erianum,  Dn.,  "  Report  on  Canadian  Plants."  1871. 
t  Type  D.  Clarkii,  Dn.,  "  Report  on  Canadian  Plants,"  1882.    This  may  be 
wood  of  Cordaites,  to  which  it  approaches  very  closely. 


Family  Coedaite^e,  Genus  Cordaites,  Brongniart. 

Trunks  marked  by  transverse  scars  of  attachment  of  bases  of 
leaves ;  leaves  broad,  with  many  parallel  veins,  and  attached  by  a 
broad  base ;  pistillate  and  staminate  catkins  of  the  nature  of  An- 
tholithes.  Fruit  winged  or  pulpy,  of  the  kind  known  as  Cardio- 
carpum.  Stem  with  a  Sternbergia  pith,  usually  large,  surrounded  by 
a  ring  of  pseudo-sealariform  vessels,  and  with  a  cylinder  usually 
narrow,  of  woody  wedges,  with  bordered  pores  in  one  or  more  series, 
and  with  simple  medullary  rays. 

From  specimens  kindly  presented  to  me  by  Prof.  Renault,  I 
have  been  able  to  ascertain  that  the  stems  of  some  at  least  of  these 
plants  (Eucordaites)  are  distinct  in  structure  from  all  the  species  of 
Dadoxylon,  above  mentioned,  except  D,  Clarkii,  of  the  Erian.  They 
may  be  regarded  as  intermediate  between  those  of  conifers  and 
cycads,  which  is  indeed  the  probable  position  of  these  remarkable 
plants. 

Grand  Eury  has  divided  the  Cordaites  into  sub-genera,  as  fol- 
lows: 

1.  Eucordaites. — Leaves  spatulate,  obovate,  elliptical,  or  Ian- 


152 


TUE  GEOLOGICAL   HISTORY  OF  PLANTS. 


i  i' 


!l  I: 


*    ! 


['■    -      h    -i- 


ceolate,  sessile,  entire,  with  rounded  apices  and  of  leathery  con- 
sistency. The  leaves  urc  from  twenty  to  ninety  centimetres  in 
length.     The  nerves  are  either  equally  or  unequally  strong. 

2.  Dorycordaites. — Leaves  lanceolate,  with  sharp  points ;  nerves 
numerous,  fine,  and  equal  in  strength.  The  leaves  attain  a  length 
of  from  forty  to  fifty  centimetres. 

3.  Poacordaites. — Leaves  narrow,  linear,  entire,  lilunt  at  the 
point,  with  nerves  nearly  equally  strong.  The  leaves  are  as  much 
as  forty  centimetres  in  length. 

To  these  Renault  and  Zeiller  have  added  a  fourth  group,  Scuto- 

cordaites. 

Oeyius  Sternbeegia. 

This  is  merely  a  provisional  genus  intended  to  receive  casts  of 
the  pith  cylinders  of  various  fossil  trees.  Their  special  peculiarity 
is  *^hat,  as  in  the  modern  Cccropia  peltata,  and  some  species  of  Ficus, 
*  •  pith  consists  of  transverse  dense  partitions  which,  on  the  elonga- 
tion of  the  internodes,  become  separated  from  each  other,  so  as  to 
produce  a  chambered  pith  cavity,  the  cast  of  which  shows  transverse 
furrows.  The  young  twigs  of  the  modern  Abies  hahamifera  pre- 
sent a  similar  structure  on  a  minute  scale.  I  have  ascertained  and 
described  such  pith-cylinders  in  large  stems  of  Dadoxylon  Oxiangon- 
dianum,  and  D.  materiarium.  They  occur  also  in  the  stems  of 
Cordaites  and  probably  of  Sigillarim.  I  have  discussed  these  curi- 
ous fossils  at  length  in  "  Acadian  Geology  "  and  in  the  "  Journal  of 
the  Geological  Society  of  London,"  1860.  The  following  summary 
is  from  the  last-mentioned  paper :  j 

a.  As  Prof.  Williamson  and  the  writer  have  shown,  many  of 
the  Sternhergia  piths  belong  to  coniferous  trees  of  the  genus  Da- 
doxylon. 

b.  A  few  specimens  present  multiporons  tissue,  of  the  type  of 
Didyoxylon,  a  plant  of  unknown  afiinities,  and  which,  according  to 
Williamson,  has  a  Sternbergia  pith. 

c.  Other  examples  show  a  true  sealariform  tissue,  comparable 
with  that  of  Lepidodendron  or  Sigillaria,  but  of  finer  texture.  Corda 
has  shown  that  plants  of  the  type  of  the  former  genus  (his  Loma- 
tophloios)  had  Ster7ibergia  piths.  Some  plants  of  this  group  are  by 
external  characters  loosely  reckoned  by  botanists  as  ribless  Sigillarm 
{Clathraria)',  but  I  believe  that  they  are  not  related  even  ordinal ly 
to  that  genus.  ' 

d.  Many  Carboniferous  Stemhergim  show  structures  identical 
with  those  described  above  as  occurring  in  Cordaites,  and  also  in 
some  of  the  trees  ordinarily  reckoned  as  Sigillarim. 


\    li 


THE  CARBONIFEROUS  FLORA. 


153 


Oenua  Cardiocarpum. 

1  have  found  at  least  eight  species  of  these  fruits  in  the  Erian 
and  Carboniferous  of  New  Brunswick  and  Nova  Scotia,  all  of  which 
are  evidently  fruits  of  gymnospermous  trees.  They  agree  in  hav- 
ing a  dense  coaly  nucleus  of  appreciable  thickness,  even  in  the 
flattened  specimens,  and  surrounded  by  a  thin  and  veinless  wing  or 
margin.  They  have  thus  precisely  the  appearance  of  samaras  of 
many  existing  forest-trees,  some  of  which  they  also  resend)le  in  the 
outline  of  the  margin,  except  that  the  wings  of  samaras  are  usually 
veiny.  The  character  of  the  nucleus,  and  the  occasional  appearance 
in  it  of  marks  possibly  representing  cotyledons  or  embryos,  forbids 
the  supposition  that  they  are  spore-cases.  They  must  have  been 
fruits  of  phtpnogams.  Whether  they  were  winged  fruits  or  seeds, 
or  fruits  with  a  pulpy  envelope  like  those  of  cycads  and  some 
conifers,  may  be  considered  less  certain.  The  not  infrequent  dis- 
tortion of  the  margin  is  an  argument  in  favour  of  the  latter  view, 
though  this  may  also  be  supposed  to  have  occurred  in  samaras  par- 
tially decayed.  On  the  other  hand,  their  being  always  apparently 
flattened  in  one  plane,  and  the  nucleus  being  seldom,  if  ever,  found 
denuded  of  its  margin,  are  arguments  in  favour  of  their  having  been 
winged  nutlets  or  seeds.  Until  recently  I  had  regarded  the  latter 
view  as  more  probable,  and  so  stated  the  matter  in  the  second  edi- 
tion of  "  Acadian  Geology."  I  have,  however,  lately  arrived  at  the 
conclusion  that  the  Cardiocarpa  of  the  type  of  C.  cornutum  were 
gymnospermous  seeds,  having  two  cotyledons  embedded  in  an  albu- 
men and  covered  with  a  strong  membranous  or  woody  tegmen  sur- 
rounded by  a  fleshy  outer  coat,  and  that  the  notch  at  the  apex  rep- 
resents the  foramen  or  micropyle  of  the  ovule.  The  structure  was 
indeed  very  similar  to  that  of  the  seeds  of  Taxus  and  of  SaUf<buria. 
With  respect  to  some  of  the  other  species,  however,  especially  those 
with  very  broad  margins,  it  still  appears  likely  that  they  were  winged. 

The  Cardiocarpa  were  borne  in  racemes  or  groups,  and  it  seems 
certain  that  some  of  them  at  least  are  the  seeds  of  Cordaites.  The 
association  of  some  of  them  and  of  those  of  the  next  genus  with 
SigillaricB  is  so  constant  that  I  cannot  doubt  that  some  of  them 
belong  to  plants  of  that  genus,  or  possibly  to  taxine  conifers.  The 
great  number  of  distinct  species  of  these  seeds,  as  compared  with 
that  of  known  trees  which  could  have  produced  them,  is  very  re- 
markable. V      '  ' 

Oenus  Trigonocarpum. 

These  are  large  angled  nuts  contained  in  a  thick  envelope,  and 
showing  internal  structures  resembling  those  of  the  seeds  of  modem 
15 


r^ 


154 


THE   GEOLOGICAL  HISTORY   OF  PLANTS 


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i 


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t..  ; 


it 


Taxinete.  There  are  numorous  species,  as  well  as  allied  seeds  re- 
ferred to  the  provisional  genera  lihahdocarpus  and  Cnrpolifhes. 
In  Trigonocarpum  Ilookeri  I  have  described  the  internal  structure 
of  one  of  those  seeds,  and  many  fine  examples  from  the  coal-field  of 
St.  Etienne,  in  France,  have  been  described  by  Brongniart,  so  that 
their  internal  structure  is  very  well  known. 

Genua  Antholithes.  , 

This  is  also  a  provisional  genus,  to  include  spikes  of  floral 
organs,  some  of  which  are  known  to  have  belonged  to  Cordaiies, 
others  probably  to  Siyillarue. 

Of  Uncertain  Affinities. 

Family  Sigillariace^. 

Under  this  name  palajobotanists  have  included  a  great  number 
of  trees  of  the  Carboniferous  system,  all  of  which  are  characterised 
by  broad  leaf-sears,  with  three  vascular  scars,  and  usually  arranged 
in  vertical  rows,  and  by  elongated  three-nerved  leaves,  and  roots  of 
the  stigmaria  type — that  is,  with  rounded  pits,  marking  the  attach- 
ment of  rootlets  spirally  arranged.  These  trees,  however,  collected 
in  the  genus  Sigillaria  by  arbitrary  characters,  which  pass  into 
those  of  the  Lepidodendroid  trees,  have  been  involved  in  almost  inex- 
tricable confusion,  to  disentangle  which  it  will  be  necessary  to  con- 
sider :  1.  The  external  characters  of  SigillaricB,  and  trees  confounded 
with  them.  2.  Subdivision  of  Sigillarice  by  external  markings.  3. 
The  microscopic  character  of  their  stems.  4.  What  is  known  of 
their  foliage  and  fruit. 

1.  Characters  of  SigiUaroid  and  Lepidodendroid  Trunks.       ■ 

It  may  be  premised  that  the  modes  of  determination  in  fossil 
botany  are  necessarily  different  from  those  employed  in  recent  bot- 
any. The  palaiobotanist  must  have  recourse  to  characters  derived 
from  the  leaves,  the  scars  left  by  their  full,  and  the  internal  struct- 
ures of  the  stem.  These  parts,  held  in  little  esteem  by  botanists  in 
describing  modern  plants,  and  much  neglected  by  them,  must  hold 
the  first  place  in  the  regard  of  the  fossil  botanist,  whereas  the  fructi- 
fication, seldom  preserved,  and  generally  obscure,  is  of  compara- 
tively little  service.  It  is  to  be  remarked  also  that  in  such  general- 
ised plants  as  those  of  the  Palspozoic,  remarkable  rather  for  the  de- 
velopment of  the  vegetative  than  of  the  reproductive  organs,  the 
former  rise  in  importance  as  compared  with  their  value  in  the  study 
of  modem  plants. 


:if. 

;ii 

III ; 


THE  CARBONIFEROUS  FLORA. 


155 


In  Sigillarife,  Lepidodendra,  &c.,  tho  following  surfaces  of  the 
stem  may  be  presented  to  our  inspection  : 

1.  The  outer  surface  of  the  epidermis  without  its  leaves,  but 
witii  the  leaf-buses  and  leaf-scars  more  or  less  perfectly  preserved. 
On  this  surface  we  may  recognise :  (1)  Celhdar  swellings  or  pro- 
jections of  tho  bark  o  which  the  leaves  are  attached.  These  may  bo 
willed  leaf-base.%  and  they  arc  sometimes  very  prominent.  (8)  Tho 
actual  mark  of  the  attachment  of  the  leaf  situated  in  the  most 
prominent  part  of  the  leaf-base.  This  is  tho  Itaf-scnr.  (3)  In  the 
leaf-scar  when  well  preserved  we  can  see  one  or  more  minute  {junct- 
ures or  prominences  which  are  the  points  where  the  vascular  bundles 
passing  to  the  leaf  found  exit.    These  are  the  vascular  scars. 

When  the  leaves  are  attached,  the  leaf-scars  and  vascular  scars 
cannot  bo  seen,  but  the  leaf-bases  can  be  made  out.  Ilenco  it  is 
important,  if  possible,  to  secure  specimens  with  and  without  the 
leaves.  In  flattened  specimens  the  leaf-bases  are  often  distorted  by 
pressure  and  marked  with  furrows  which  must  not  be  mistaken  for 
true  structural  characters.  The  leaf-bases,  which  are  in  relief  on  tho 
outer  surface  of  the  stem,  of  course  appear  as  depressions  on  the 
mould  in  the  containing  rock,  in  which  the  markings  often  appear 
much  more  distinctly  than  on  the  plant  itself. 

2.  Tho  outer  surface  of  the  epidermis  may  have  been  removed  or 
may  be  destroyed  by  the  coarseness  of  the  containing  rock.  In  this 
case  the  leaf-bases  are  usually  preserved  on  the  surface  of  the  outer 
or  corky  bark,  but  the  leaf-scars  and  vascular  scars  have  disappeared. 
This  gives  that  condition  of  Lepidodendroid  trees  to  which  the  name 
Knorria  has  been  applied.  When  plants  are  in  this  state  careful  in- 
spection may  sometimes  discover  traces  of  the  leaf-scars  on  portions 
of  the  stem,  and  thus  enable  the  Knorria  to  be  connected  with  the 
species  to  which  it  belongs. 

3.  The  outer  or  corky  bark  may  be  removed,  exposing  the  sur- 
face of  the  inner  or  fibrous  and  cellular  bark,  which  in  the  plants  in 
question  is  usually  of  great  thickness.  In  this  case  neither  the  leaf- 
bases  nor  the  scars  are  seen,  but  punctures  or  little  furrows  or  ridges 
appear  where  the  vascular  bundles  entered  the  inner  bark.  Speci- 
mens in  this  state  are  usually  said  to  be  decorticated,  though  only 
the  outer  bark  is  removed.  It  is  often  dilficult  to  determine  plants 
in  this  condition,  unless  some  portion  of  the  stem  can  be  found  still 
retaining  the  bark ;  but  when  care  is  taken  in  collecting,  it  will  not 
infrequently  be  found  that  the  true  outer  surface  can  be  recovered 
from  the  containing  rock,  especially  if  a  coaly  layer  representing  the 
outer  bark  intervenes  between  this  and  the  inner  impression.    Speci- 


III 


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L56 


THE  GEOLOGICAL  HISTORY  OF  PLANTS 


mens  of  this  kind,  taken  nlone,  have  been  referred  to  the  genera 
Knorria,  Bnthrodendron,  and  Ilalonia. 

4.  In  some  cases,  though  not  frequently,  the  outer  surface  of  the 
ligneous  cylinder  is  pri'scrved.  It  almost  invariably  presents  a 
regularly  striated  or  irregularly  wrinkled  appearance,  depending 
upon  the  vertical  woody  wedges,  or  the  positions  of  the  medullary 
rays  or  vascular  bundles.  Specimens  of  this  kind  constituted  some 
of  the  Endogenites  of  the  older  botanists,  and  the  genus  Schizoden- 
dron  of  Eichwald  appears  to  include  some  of  them.  ^lany  of  them 
have  also  Iwen  incorrectly  referred  to  Calamites. 

5.  In  some  cases  the  cast  of  the  medullary  cylinder  or  pith  may 
alone  be  preserved.  This  may  be  nearly  smooth  or  slightly  marked 
by  vertical  striro,  but  more  usually  presents  a  transverse  striation, 
and  not  infrequently  the  transverse  constricticms  and  septa  charac- 
teristic of  the  gonus  Stembergia.  Ijoosc  Sternhergice,  alTord  little 
means  of  connecting  them  with  the  species  to  which  they  belong, 
except  by  the  microscopic  examination  of  the  shreds  of  the  ligneous 
cylinder  which  often  cling  to  them.* 

These  facts  being  premised,  the  following  general  statements 
may  be  made  respecting  some  of  the  more  common  Palaeozoic  genera, 
referring,  however,  principally  to  the  perfect  markings  as  seen  on 
the  epidermis : 

Sigillaria, — Leaf-bases  hexagonal  or  el  ngated,  or  confluent  on 
a  vertical  ridge.  Leaf-scars  hexagonal  or  shield-shaped.  Vascular 
scars  three,  the  two  lateral  larger  than  the  central.  This  last  char- 
acter is  constant,  depending  on  the  fact  that  the  leaves  of  Sigillaria 
have  two  or  more  vascular  bundles.  All  so-called  Sigillarim  having 
the  central  vascular  scar  largest,  or  only  one  vascular  bundle,  should 
bo  rejected  from  this  gonus.  In  young  branches  of  branching  Sigil- 
larim  the  leaf -scars  sometimes  appear  to  be  spiral,  but  in  the  older 
stems  they  form  vortical  rows;  interrupted,  however,  by  transverse 
rows  or  bands  of  fruit-scars,  each  with  a  single  large  central  vascular 
scar,  and  which  have  borne  the  organs  of  fructification.  Arthro- 
caulis  of  McCoy  is  founded  on  this  peculiarity. 

Syringodendron. — Differs  from  Sigillaria  in  the  leaf-scars,  which 
are  circular  and  with  a  single  vascular  bundle.  It  is  a  matter  of 
doubt  whether  those  plants  were  of  higher  rank  than  Sigillaria 
tending  toward  the  pines,  or  of  lower  rank  tending  toward  Cyclo- 
stigma.    Their  leaf-bases  form  vertical  ridges. 

Lepidodendron. — Leaf-bases  rhombic,  oval,  or  lanceolate,  moder- 

♦  See  my  paper,  "  Journal  of  Geological  Society,"  vol.  xxvii. 


i 


TUE  OARBCNIFEROUS  FLORA. 


157 


ately  prominent.  Ijcai-scara  rhombic  or  sometimes  shield-shaped  or 
heart-shaped,  in  the  niddle  or  upper  part  of  the  leaf-base.  Vascular 
sears  three — the  middl'^  one  always  largest  and  corresponding  to  the 
single  nerve  of  the  leaf ;  the  lateral  ones  sometimes  obsolete. 

In  older  stems  three  modes  of  growth  are  observed.  In  some 
species  the  expansion  of  the  bark  obliterates  the  leaf-bjises  and 
causes  the  leaf-scars  to  appear  separated  by  wide  spaces  of  more  or 
less  wrinkled  bark,  which  at  length  becomes  longitudinally  furrowed 
and  simulates  the  ribbed  character  of  Sigillaria.  In  oiners  the  leaf- 
bases  grow  in  size  as  the  trunk  expands,  so  that  even  in  large  trunks 
they  are  contiguous  though  much  larger  than  those  on  the  branches. 
In  others  the  outer  bark,  hardeinng  at  an  early  age,  is  incapable  of 
either  of  the  above  changes,  and  merely  becomes  cleft  into  deep  fur- 
rows in  the  old  trunks. 

Lepidophloios. —  Leaf -bases  transverse  and  prominent  —  often 
very  much  so.  Leaf-scars  transversely  rhombic  or  oval  with  three 
vascular  scars,  the  central  largest.  Leaves  very  long  and  one- 
nerved.  Large  strobiles  or  branchlets  borne  in  two  ranks  or  spirally 
on  the  sides  of  the  stem,  and  leaving  large,  round  scars  {cone-scars), 
often  with  radiating  impressions  of  the  basal  row  of  scales. 

Species  with  long  or  drooping  leaf-bases  have  been  included  in 
Lepidophloios  and  Lotnaiophloios.  Species  with  short  leaf-bases  and 
cone-scars  in  two  rows  have  been  called  Ulodendron,  and  some  of 
them  have  been  included  in  Sigillaria  (sub-genus  Clathraria).  De- 
corticated stems  are  Bothrodendron  and  Ilalonia.  Some  of  the 
species  approach  near  to  the  last  genus,  especially  to  the  Lepidoden- 
dra  with  rhombic  leaf-bases  like  L.  tefragonum. 

Cyclosfigma.  —  Leaf-bases  undeveloped.  Leaf-scars  circular  or 
horseshoe-shaped,  small,  with  a  central  vascular  scar.  In  old  trunks 
of  Cyclostigma  the  leaf-scars  become  widely  separated,  and  some- 
times appear  in  vertical  rows.  Young  branches  of  Lepidodendron 
sometimes  have  the  leaf-scars  similar  to  those  of  Cyclostigma. 

Leptophleum.  —  Leaf -bases  flat,  rhombic  ;  leaf-scars  obsolete ; 
vascular  scar  single,  central.  The  last  t"'o  genera  are  character- 
istically Devonian. 

In  contradistinction  from  the  trees  above  mentioned,  the  follow- 
ing general  statements  may  be  made  respecting  other  groups: 

In  conifers  the  leaf-bases  are  usually  elongated  vertically,  often 
scaly  in  appearance,  and  with  the  leaf -scar  terminal  and  round,  oval, 
or  rhombic,  and  with  a  single  well-marked  vascular  scar. 

In  Calamites,  Calamodendron,  and  Asterophyllites  the  scars  of 
the  branchlets  or  leaves  are  circular  or  oval,  with  only  a  single  vas- 


! 


IT 

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158 


TUE  GEOLOGICAL   HISTORY  OF  PLANTS. 


cularscar,  and  situated  in  verticils  at  the  top  of  well-marked  no  leg 
of  thi;     'iin. 

In  trcc-fcrns  the  leaf-bases  are  largo  and  usually  withou„  a  dis- 
tinct articulating  surf»«ie.  The  vascular  l)undles  are  numerous. 
Protopteris  has  round(!d  leaf-scars  with  a  large  hf)rseshoc-  haped 
bundle  of  vessels  above  and  sniuU  bundles  l)olow.  Oaulopteris  has 
large  elliptic  or  oval  leaf-scars  with  vascular  scars  disposed  con- 
centrically. Pal^opteris,*  of  Geinitz,  has  the  leaf-scars  transversely 
oval  and  the  vascular  bundles  confluent  in  a  transverse  band  with  an 
appendage  or  outlying  bundle  below.  Stemmatopteris  has  leaf- 
scars  similar  to  those  oi  Cauloptcris,  but  the  vascular  bundles  united 
into  a  horseshoe-shaped  band. 

2.  Subdii'iHion  of  Sicjillarim  in  Accordance  with  their  Marldngs. 

The  following  groups  maybe  defined  in  this  way;  but,  being 
based  on  one  cluiracter  only,  they  are  of  course  in  all  probability  far 
from  natural :  '  ■ 

1.  Siyillarin,  Brongniart.  Type,  Sigillaria  reniformis,  Bron- 
gnijirt, or  S.  lirounii,  Dawson. — Stem  with  broad  ribs,  usually  mtu'h 
broader  than  the  usually  oval  or  elliptical  tripunctate  areoles,  but 
disappearing  at  base,  owing  to  expansion  of  the  stem.  Leaves  nar- 
row, long,  three-nerved. 

2.  RhytidolcpiH,  Sternberg.  Type,  S.  scuMlnta,  Brongniart. — 
Ribs  narrow,  and  often  transversely  striate.  Areoles  large,  hexag- 
onal or  shield-shaped,  tripunctate.  Leaves  as  in  last  group.  Rings 
of  rounded  scars  on  the  stems  and  branches  mark  attachment  of 
fruit.  It  is  i)ossibIe  that  some  of  the  smaller  stems  of  this  group 
niay  be  branches  of  trees  of  group  first. 

3.  Syrinjiodendron,  Sternberg.  Type,  S.  organnm,  L.  and  IT., 
S.  oculala,  Brongniart.. — Stems  r* '  -^d ;  areol»>s  small  and  round, 
and  apparently  with  a  single  scar,  ,,  three  closely  approximated. 
These  are  rare,  and  lial)l(!  to  l)e  confounded  with  decorticated  ex- 
amines of  other  groups ;  l)ut  I  have  some  specimens  which  unques- 
tionably represent  the  external  surface. 

4.  Fdi'ulnria,  Sternberg.  Type.  Sigillaria  chgnns  of  Brongni- 
art.— Leaf-bases  hexagonal,  or  in  young  branches  elliptical,  in  vertical 
rows,  but  without  distinct  ribs,  except  in  old  or  decor* icated  stems. 
Fruit  borne  in  verticils  on  the  nran<!hes  l«'aring  transverse  rows  of 
rounded  scars.     Leaves  somewhat  broad  and  longitudmally  .striate. 


*  This  name,  preocciinied  by  Geinitz,  has  been  inadvertently  misap- 
plied to  the  Dcvouiau  ferae  of  the  genuti  ArcJueoptcris. 


i!i 


THE  CARBONIFEROUS  FLORA, 


159 


6.  Leioderma,  Goldonborf?.  Type,  S,  Sydjiermis,  Dawson.  — 
Ribs  obsolete.  Cortical  and  ligneous  surfaces  strh^o.  Vascular 
scars  double.  elonf,'atc  loti^itudiniilly,  and  alike  on  co:(ical  and  inner 
surfaces.  Areoles  in  rows  and  distinct;  stigmaria-roots  striate, with 
small  and  distinct  areoles. 

•  6.  ('Inthrnrin,  Hron^jniurt.  Type,  aS".  Mennrdi,  Brongniart. — 
Areoles  li(!XHf,'()nuI,  iiot  in  distinct  rows,  but  havinp^  a  spiral  apjjcar- 
ance.  Some  of  tlie  |)lunts  ustuilly  referred  to  this  j^roup  are  probalily 
branches  of  Favularia.  (Jthers  are  evidently  fragments  of  plants 
of  the  genus  Lepidojihloios. 

S.  Internal  Structures  of  Sujillaria-StemH. 

1  long  a^jo  pointed  out,  on  the  evidence  of  the  external  markings 
and  mode  of  growth,  that  the  stems  of  Sigillarim  must  have  been 
exogenous,  and  this  conclusion  has  now  been  fully  confirmed  by  the 
microscopic  researches  of  VVillianison,  not  only  in  the  case  of  >SV/yi7- 
lariiB,  but  of  Lepidodetidra  and  ( 'alamodendra  as  W(!ll.  (-'onfining 
myself  to  my  own  observations,  three  types  of  Siffillanai  are  known 
to  me  l)y  their  internal  structures,  though  I  cannot  certainly  corre- 
late all  of  these  with  the  exter.ial  markings  referred  to  above. 

1.  Diplnxylon,  in  which  the  stem  consists  of  a  snuUl  internal 
axis  surrounded  by  a  very  thick  inner  bark  and  a  dcmse  outer  cortex. 
A  fine  example  from  the  South  Joggins  is  thus  described :  * 

"The  axis  of  the  stem  is  about  six  centimetres  in  its  greatest 
diameter,  and  consists  of  a  central  pith-cylinder  and  two  concen- 
tric coats  of  scalariform  tissue.  The  pith-cylinth^r  is  replaced 
by  sandstone,  and  is  about  one  centimetre  in  diameter.  The  inner 
cyliiuh^r  of  scalarifortn  tissue  is  perfectly  continuous,  not  radiated, 
and  about  one  millimetn!  in  thickness.  Its  vessels  arc  somewhat 
crushed,  but  have  liecn  of  large  diameter.  Its  outer  surface,  which 
readily  separates  from  that  of  the  outer  cylinder,  is  striated  longi- 
tut";  lal'y.  The  outer  cylinder,  which  institutes  by  much  the 
largest  part  of  the  whole,  is  also  compose(l  of  scalariform  tissue; 
but  thin  is  radially  arranginl,  with  the  individual  cells  (jua<lraiigular 
in  cross-section.  The  cross-bars  are  similar  f>Ti  all  the  sides  and 
usually  simple  and  straight,  but  sometimes  l)ranching  or  slightly 
reticulated.  The  wall  intervening  between  the  bars  has  extremely 
delicate  longitviclinal  waving  lines  of  ligneous  lining,  in  th(!  manner 
first  described  by  Williamson  as  occurring  in  the  scalariform  tissue 
of  certain  Lepidodendra.     A  few  small  radiating  spaces,  partially 


•  "  Journal  of  the  Geological  Society  of  London,"  Novciuber,       '7. 


1  I 


I ' 


,i  lil  I 


r   : 


IGO 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


occupied  witli  pyrites,  obscurely  represent  the  medullary  rays,  which 
must  have  l»cen  very  feebly  developed.  'J'ho  radiating  bundles 
passing  to  the  leaves  run  nearly  horizontally ;  but  their  structure 
is  very  imrcrfecttly  jjreserved.  'J'ho  stem  Ijeing  old  and  probably 
long  deprived  of  its  leaves,  they  may  have  been  partially  disorganised 
before,  it  was  fossilised.  TIk;  outer  surface  of  th(!  axis  is  slriaU'd 
longitudiiuilly,  and  in  some  places  marked  with  imfircssions  of  tort- 
uous libres,  apf)ar(!ntly  those  of  the  inner  bark,  in  the  cross-sec- 
tion, where  weathered,  it  shows  concentric  rings;  but  under  the 
mi(!roscop(!  thes(!  ai)p<'ar  rather  as  bands  of  compressed  tissue  than 
as  proper  lines  of  growth.  They  are  alxjut  twenty  in  iiumlM'r.  This 
tree  has  an  erect,  ribbed  trunk,  twelve  feet  in  height  and  fifteen 
inches  in  diameter,  swc^lling  to  about  two  feet  at  the  base. 

2.  Fdi'iilurid  'J'ypc. — This  has  been  well  described  by  Urongniart 
and  by  Renault,* and  dilTers  from  the  above  chiefly  in  the;  fact  that 
the  outer  exogenous  woody  zoiu;  is  comi)os('d  of  reticulatc.'d  instead 
of  scalariform  li-.iue,  and  the  inner  /one  is  of  the  peculiar  form 
which  1  have  (iharacterised  as  pseudo-scalariform. 

8.  Siyillaria  l*ropcr. — This  I  have,  illustrated  in  my  paper  in 
the  "Journal  of  the  Geological  Society"  for  May,  1H71,  and  it  ap- 
peal's to  repnist^nt  the  highest  and  most  perfect  type  of  the  larger 
riblied  Sujillarin.  1'his  structure;  I  have;  (les(;ribed  as  follows,  bas- 
ing my  descrij)t  ion  on  a  very  lim;  axis  found  in  an  erect  stem,  and 
on  the  fragments  of  the  woody  axis  found  in  the  bases  of  other  erect 
stems : 

a.  A  dense  ct ''...lar  outer  bark,  usually  in  the  slate  of  compact 
coal — but  wh(  II  its  structure  is  preserved,  showing  a  tiH.sue  of  thick- 
ened parenchymatous  cells.  • 

h.  A  very  thick  inner  bark,  which  has  iismilly  in  great  part 
perished,  or  been  converted  into  (!oal,  but  which,  in  old  trunks,  con- 
tained a  large;  <|uantity  of  prosenehymatous  tissue,  very  tough  and 
of  great  durability.  This  "bast-tissue"  is  comparable  with  that  of 
the  inner  bark  of  modern  conifers,  and  constitutes  much  of  tiie  min- 
eral charcoal  of  the  coal-seams, 

c.  An  outer  ligneous  cylinder,  composed  of  wood-cells,  (lither 
with  a  single  row  of  larg(!  bordered  [)ores,f  in  the  numtier  of  pines 

*  "Uotani(pie  Fossile,"  Paris,  1881. 

f  These  are  the  same  with  the  wood-cells  elsewhere  called  diHcigorouB 
tissue,  and  to  which  I  have  applied  the  terms  unipoious  and  multiporoua. 
The  markings  on  the  walls  are  caused  by  an  unlincd  p  ,.tion  of  the  cell- 
wall  placed  in  a  disk  or  depression,  and  this  often  surrounded  by  an 


THE  CARBONIFEROUS  FLORA, 


ir,i 


and  cycads,  or  with  two,  three,  or  four  rows  of  siioh  pores  sometimes 
inscribed  in  hexagonal  areoles  in  the  manner  of  Mu/orv/ora,  This 
woody  cylinder  is  traversed  \>y  medullary  rays,  which  tire  short,  and 
composed  of  f(!W  rows  of  ca-Ws  su[U'riinposed.  It  is  also  traversed  by 
ol)li(pio  radiating  bundles  of  pseudo-sealariform  tissue  proceeding  to 
the  leaves.  In  soiu(!  Sit/if/nrun  this  outer  cylinder  was  iiself  in  part 
com[)osed  of  pscudo-sciilariform  tissue,  as  in  Jirongniart's  specimen 
of  .S'.  elcf/aiiM ;  and  in  others  its  plucc;  may  have  l)een  taken  by  mul- 
tiporous  tissue,  as  iti  a  case  alK)ve  n^ferred  to ;  but  I  have  no  reason 
to  Ixdieve  that  either  of  these  variations  occurred  in  the  typical 
ribbed  sjiecic^s  now  in  question.  Tfie  woody  filires  of  the  outer 
cylinder  nuiy  b(?  distinguished  most  readily  from  tliosi;  of  conifers, 
as  already  mentioncid,  by  the  thinness  of  their  walls,  and  the  more 
irregular  distribution  of  the  pores.  Additional  charact(!rs  are  fur- 
nished by  the  nietlidlary  rays  and  the  radiating  bundles  of  8calari- 
form  tissues  when  these  can  be  observed. 

d.  An  innifr  cylinder  of  ps(!udo-scalariform  tissue,  I  have 
adopted  the  term  ftseudo-scidariform  for  this  tissue,  from  the  con- 
viction that  it  is  not  liortiologous  with  the  scalar! fffrri'  ducts  of  ferns 
and  other  acrogi'iis,  but  that  it  is  merely  a  modification  of  tin;  dis- 
c ,gerf)us  wood-cells,  wit  h  pores  elongated  t  ransversely,  and  sonuitimes 
separated  by  thic^kened  bars,  corres{)onding  to  the  hexagonal  areo- 
lation  of  the  ordinary  wood-cells.  A  similar  tissut;  exists  in  cycads, 
and  is  a  substitutt;  for  the  spiral  vcssc^ls  existing  in  (ordinary  ex- 
ogens. 

e.  A  large  medulla,  or  pith,  consisting  of  a  hollow  cylinder  of 
cellular  tissue,  from  which  proceed  numc^rous  thin  diaphragms  to- 
wards the  cent  Hi  of  the  stem. 

These  structures  of  the  highest  type  of  Sigillaria  are  on  the 
one  hand  scarcely  advanced  b(!yond  those  of  (JalninnpHun,  as  de- 
scribed by  Williamson,  and  on  the  other  a[)proach  to  those  of 
(jordaitPH,  as  seen  in  specimens  presented  to  mr-  by  Renault. 

Finally,  as  to  the  fruit  of  JSir/illarid',  I  Imvo  no  new  facts  to 
ofT(!r.  The  strobiles  or  sjiikes  associated  with  these  trees  have  Ijcen 
variously  described  as  gymno.^permous  (]((;nault)  or  cryptogamous 
((loldenberg  and  Williamson).  I  have  never  seen  them  in  plaoe. 
Two  considerations,  however,  have  always  weighetl  with  me  in  refer- 
ence to  this  subj(!ct.     One  is  the  constant  abundance  of  Trigotiocarpa 


hexagonal  rim  of  thickenod  wall ;  but  in  all  cases  these  Htnicturcs  arc 
less  pionoimeed  than  in  I)tiilori//i>n,  and  less  regidar  in  tlie  walls  of  the 
liuiiie  ceil,  aa  well  us  in  dilTcrcnt  layers  of  the  tiesucs  of  the  axia. 


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''■:■  n 

I;  i" 


1C2 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


and  Cardiocarpa  in  the  soil  of  the  Sigillaria  forests,  as  I  have  st»idied 
this  at  the  South  Jogj^ins.  The  other  is  that  the  rings  of  fruit-scars 
on  the  branches  of  Sigillaria  are  homologous  with  leaf-soars,  not 
•with  branches,  and  therefore  should  have  borne  single  carpels  and 
not  cones  or  spikes  of  infloresceiice.  These  ai"e  merely  suggestions, 
lit  I  have  no  doubt  they  will  be  vindicated  by  future  discoveries, 
which  will,  I  have  no  doubt,  show  that  in  the  family  SigillariacecB 
we  have  really  two  families,  one  possibly  of  gymnospermous  rank, 
or  at  least  approaching  to  this,  the  other  allied  to  the  Lepidodendra. 

Cryptooamia. 

{Acrogenes.) 

Family  Lepidodendrkte  ;  Oenua  Lepidodexdron,  Sternberg. 

These  arc  arboreal  Lycopods  having  linear  one-nerved  leaves, 
stems  branching  dichotoiiiously,  and  with  ovate  or  rhombic  leaf-bases 
bearing  rhombic  leaf-scars,  often  very  prominent.  The  fiuit  is  in 
scaly  strol)iles,  terminal  or  lateral,  and  there  are  usually,  if  not 
always,  macrospores  and  microspores  in  each  strobile.  The  young 
branches  and  stems  have  a  central  pith,  a  cylinder  of  scalariform 
tubes  sending  out  ascending  bundles  to  the  leaves  through  a  thick 
cellular  and  fibrous  inner  bark,  and  externally  a  dense  cortex  conflu- 
ent with  or  consisting  of  the  leaf-bases.  Older  stems  have  a  second  or 
outer  layer  of  scalariform  fil)res  in  wedges  with  medullary  rays,  and 
strengthening  the  stem  l)y  a  true  c  oogenous  growth,  much  as  in  the 
Diploxylon  typo  of  Sigillaria.  The  development  of  this  exogenous 
cylinder  is  different  in  amount  and  rate  in  different  species.*  This 
different  development  of  the  exogenous  axis  is  accompanied  with 
appropriate  external  appearances  in  the  stems,  and  the  changes 
which  take  place  in  tlieir  nuirkings.  These  are  of  three  kinds.  In 
some  species  the  areoles,  at  first  close  together,  become,  in  the  pro- 
cess of  the  expansion  of  the  stem,  separated  by  intervening  spaces  of 
bark  in  a  perfectly  regular  matmer ;  so  that  in  old  stems,  while  widely 
separated,  they  still  retain  tlieir  arrangement,  while  in  young  stems 
they  are  (piite  close  to  one  another.  This  is  the  case  in  L.  corruga- 
tum.  In  other  species  the  leaf-scars  or  bases  increase  in  size  hi  the 
c'd  stems,  still  retaining  their  forms  an<l  their  contiguity  to  each 
other.  Tills  is  the  case  in  />.  uiululatum,  and  generally  in  those 
Lt'2,^dudtndra  which  have  large  leaf-bases.     In  these  species  the 


*  See  "  Memoirs  of  Dr.  Williamson,"  in  "  Philosophical  TranHactlons," 
for  ample  details. 


THE  CARBONIFEROUS  FLORA. 


163 


continued  vitality  of  the  bark  is  shown  by  the  occasional  production 
of  lateral  strobiles  on  large  branches,  in  the  manner  of  the  modem 
red  pine  of  America.  In  other  species  the  arcoles  neither  increase  in 
size  nor  become  regularly  separated  by  growth  of  the  intervening 
bark ;  but  in  old  stems  the  bark  splits  into  deep  furrows,  between 
which  may  bo  seen  portions  of  bark  still  retaining  the  areoles  in 
their  original  dimensions  and  arrangement.  This  is  the  case  with 
Jj.  Pictopn.ie.  This  cracking  of  the  bark  no  doubt  occurs  in  very  old 
trunks  of  the  first  two  types,  but  not  at  all  to  the  same  extent. 

As  a  type  of  Lepidodendron,  1  may  describe  one  of  the  oldest 
Carboniferous  species  characteristic  of  the  Lower  Carboniferous  in 
America,  and  corresponding  to  L.  Ydtheimianum  of  Kurope. 

LEPrDODE>fDRON  CoRRuoATUM,  Dawson. — (See  Fig,  4:5,  snjrrn.) 
"  Quarterly  Journal  of  Geological  Society,"  vol.  xv. ;  "  Acadian  Geol- 
ogy," page  451. 

Habit  of  Orowth. — Somewhat  slender,  with  long  V)ranches  and 
long,  slender  leaves  having  a  tendency  to  become  horizontal  or 
drooping. 

Markings  of  Stem. — Leaf-bases  disposed  in  quincunx  or  spirally, 
elongate,  ovate,  acute  at  both  ends,  l)Ut  more  acute  and  slightly 
oblique  at  the  lower  end ;  most  prominent  in  the  iq)per  third,  and 
with  a  slight  vertical  ridge.  Leaf-scars  small,  rounded,  and  showing 
only  a  single  punctiforin  vascular  scar.  The  leaf-scar  on  the  outer 
surface  is  in  the  \q)per  third  of  the  base;  but  the  obliquity  of  the 
vascular  bundle  causes  it  to  be  nearly  central  on  the  inside  of  the 
epidermis.  In  young  succulent  shoots  the  leaf-scars  are  contiguous 
and  round  as  in  Cyclostigma,  without  distinct  leaf-bases.  In  this 
state  it  closely  resembles  L.  Olivieri,  Kichwald.* 

In  the  ordiiuiry  yoimg  branches  the  leaf-si  ars  are  contiguous, 
and  closely  resemble  those  of  L.  ehgann,  IJrongt.  (Fig.  43  C).  As  the 
branches  increase  in  diameter  the  leaf-scars  slightly  enlarge  and 
sometimes  assume  a  vcrticillate  appearance  (Fig.  413  D).  As  they 
still  furtluir  enlarge  they  become  scpiinittMl  by  gradually  increasing 
spaces  of  bark,  marked  with  many  waving  stritc  or  wrinkles  (Fig. 
43  I,  N).  At  the  base  of  old  stems  the  bark  assumes  a  gfjni'rally 
wrinkled  appearance  without  distinct  scars. 

Kiwrria  or  Decorticated  States. — Of  these  there  is  a  great  variety, 
depending  on  the  state  of  preservation,  and  the  particular  longi- 
tudinal ridges.  Fig.  43  I)  shows  a  form  in  which  the  vascular  bun- 
dles appear  as  cylindrical  truncate  projecti'-ns.     Other  forms  show 


*  Lethaea  Rossica,  Plato  Y,  Figs.  12,  18. 


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THE  (iEOLOGICAL  HISTORY  OF  PLANTS. 


tho  loaf-hasPH  promiiicni,  or  liave  un  a|)pfiarance  of  longitudinal  rib- 
bin;^  prodiicMMl  hy  Mh!  t!X|)aiisiori  of  tho  bark. 

HlrurAure  of  Stem. — This  is  not  porfnctly  prcscrvod  in  any  of 
my  Hix'ciinctiH,  l)iit  oni;  flattciu'd  .sp((c-iinon  .shows  a  central  medulla 
with  a  iijirrow  ring  of  scalariform  vtisscils  surrounding  it,  and  consti- 
tuting the  woody  axis.  The  structure  is  thus  siniilar  to  that  of  L. 
Jlarcourtii,  which  I  regard  as  i)rol)ably  tho  same  with  tho  closely 
allifid  l<iUroi)ean  species  Jj.   Vcllhnmidimm, 

L"(ivfn, — These  are  luirrow,  one-nerved,  curving  somewhat  rap- 
idly outward  (Figs.  4JJ,  li,  C,  \)).  They  vary  fr<jm  one  to  two  inches 
iti  length. 

Hoo/h. — I  hav(!  not  seen  these  actually  attached,  but  they  occur 
very  abundantly  in  the  underclays  of  some  en^ct  fonists  of  these 
plants  at  Horton  Hlulf,  and  an;  of  the  character  of  Stiijmnrid;  (FigH. 
yo,  HI).  In  some  of  the  underclays  the  long,  flattxaied  rootlets  are  ex- 
cessivcily  altundant,  and  show  tlu;  mark  of  a  central  vascular  bundle. 

Fruclijicaliun. — (.'onr^s  terminal,  short,  with  many  snudl,  acuto 
imltricate  Hcal(;s.  S|)ore-cas(!s  globular,  smooth  (Fig.  41}  ("j.  i)i\ 
tho  surface  of  some  shales  and  sandston(!s  at  Ilorlon  there  arc  innu- 
m(!rable  round  spore-c.-ases  of  this  tree  about  the  size  of  mustard-seed 
(Fig.  4;{  I'').  Iiarg(f  slabs  are  somcrtinufs  covered  with  these,  and  thin 
layers  of  shale  are  lllhid  with  flattened  sp(!cimens. 

This  is  the  characteristic  sfxsciesof  the  Lower  (-arbonif(!rf)US  coal- 
measures,  occurring  in  gnat  profusion  at  Morton  HIulI  and  its 
vicinity,  also  at  Sneid's  Mills  near  Windsor,  Noc;!  and  Five-Milo 
River,  at  Norton  ('reek  and  elsewhere  in  N(!w  Hrunswick  (Matthew's 
collection),  and  ;  .,  Antigonish  (Iloneyman's  collection). 

1  have  receiviid  from  the  lowest  ('arboniferous  beds  of  Ohif)  speci- 
mens of  this  speei(!S.*  Ac(;ordirig  to  Rogers  and  Lestjuereux  similar 
forms  occur  in  the  Ves[)ertine  of  Pennsylvania  and  in  the  Lower 
Carboniferous  of  Illinois.  Jj.  Vdthe,imi(inum  of  western  Europe 
and  L.  (jlincanum  of  Russia  are  closely  allied  Lower  Carboniferous 
spe(!i(!S.f 

A  v(!ry  different  tyi)e  is  furnislx'd  liy  a  new  species  from  the 
middle  coal-formati(jn  of  Clifton,  N(;w  Ibunswi(!k. 

Les'IUodkndron  Cliktonknsk,  Dawson.  —  JIahit  of  Growth. — 
Robust,  with  thick  branch(!s,  and  leaves  several  inches  in  length. 
Terminal  branches  becoming  slender,  with  shorter  leaves. 


*  "Journal  of  (Jeological  Society,"  November,  1862,  p.  31.3. 
f  For  conipariHons  of  these  sec  "  Report  on  IMuuts  of  Lower  Carbon- 
iferous of  Canada,"  jt. '21. 


;,u: 


frj 


THE  CARBONIFEROUS  FLORA. 


165 


thu 


MarkinfjH  of  Sfrm. — Ij('iif-l)asfts  lonj?  f)val,  pf>ititfi(l  ut  erxls,  on- 
liirfxirig  with  growth  <>!  aU'in.  Lwif-scurs  contrul,  rhornhic,  trans- 
vor,s«. 

LenvpH. — Orift-rKTvcd,  ntnitcly  pointed,  from  four  inchos  in  hiiigth 
on  tlif!  iarj^cr  hrancJics  to  one  inch  or  less  on  thf;  braruihict.s. 

FnirlificalioH, — C'orutH  larf^e.  cyiindrifal  or  lon^  oval,  with  larp^o 
Hcales  of  tri^^onal  form,  and  not  (!lf)nKat('d  but  iyiii;?  <;1ok(!  to  the  sur- 
face.    IJornc  on  lateral,  slendtT  hranchlets,  with  Hhort  leaves. 

OenuH  Iji:i'inoi'iii,oio.s,  StcrnbiTi,';  ri.oiiKNUKoN,  L,  and  II.; 
LoMAToi'Hi.o/os,  (.'ordu. 

LcpidophloioH. — Under  this  gciiuirifj  name,  established  by  Stern- 
berg^, I  include  those  Ivcojjodiaceous  trees  of  the  coal-measures 
which  hav(!  thick  branches,  transvcirsely  e!on{,'at(!(l  leaf-scars,  eiu;h 
with  three  vascular  j)oints  and  phuied  on  elevated  or  scale-like  pro- 
tulM!ratices,  long  on»!-nerv(!d  leaves,  and  larfje  lateral  strol)il(;s  in  vc^r- 
tloal  rows  or  spirally  disposed.  Tlu-'ir  strur/ture  reseirdiles  that  of 
Lfpidwictidron,  consisting?  of  a  Sli'rnbcrfjid  pith,  a  slemler  axis  of 
large  scalariforrn  vessels,  giving  off  from  its  surfac*;  biiiidh^s  of 
smaller  vesscsls  to  the  leaves,  a  very  thi<:k  c<'llular  bark,  atid  a  thin 
dense  out<!r  bark,  having  some  elongated  cells  or  l)ast-tissuc  on  its 
inner  side.  In  these  tnses  the  exogenous  outer  (cylinder  is  less  de- 
veloped tlwui  in  the  Lcpidodendra,  and  is  sometiin(!s  wanting  in 
stems  or  branches  of  some  thickness. 

Jtegarding  L.  laricinum  of  Sternberg  as  the  ty[)C  of  the  genus, 
and  taking  in  connection  with  this  the  species  described  by  (loldc'n- 
Iwrg,  and  my  own  obs(Tvations  on  num(;rous  s[)ecimens  found  in 
Nova  Scotia,  I  have  no  d<;ubt  that  LorndlophloioH  cruHHiaiuliH  of 
Corda,  and  other  species  of  that  g(!nus  described  by  Ooldenberg, 
U lodi'.ndron  and  Jiothrodcndron  of  Lindley,  Jjcpidodcndron  ornatis- 
aimum  of  IJrongniart,  and  I/rdonin  ptuiclata  of  (icinilz,  all  Iw^long 
to  this  genus,  and  differ  from  each  otlutr  only  in  conditions  of 
growth  and  pn;servation.  Several  of  the  ^)^'.i•'\^\n  of  LopidoHtrobua 
and  Lcpidophylliim  also  belong  to  Lepidophloion, 

The  species  of  Lrpiilo/t/doios  are  rca<Iily  flistiiiguisheil  from 
Lepidddcndi'on  by  the;  form  of  t  he  arcoles,  and  by  the  round  scars  on 
the  stem,  whi«'h  usually  nuirk  the  insertion  of  the  large  strobiles* 
though  in  barren  stems  they  may  also  have  produced  branches;  still, 
the  fact  of  my  finding  the  strobiles  in  hi'/u  in  (,n(;  instance,  the  ac- 
curate resemblance  which  the  scars  bear  to  those  left  by  the  cones  of 
the  red  pine  when  l)orne  on  thick  branches,  and  the  actual  im[)res- 
fiions  of  the  radiating  scales  in  some  specinien;},  leave  no  doubt  in  my 

16 


1^  . 


Il 


ill  I 


[If 

H 


I 


'! 


ifir, 


TIIR   OEOLOOrCAL   HISTORY  OF  PLANTS. 


mind  tliiit  Micy  an;  usiinlly  the  niiirUs  f)f  cones;  uiid  the  ^rcfut  size  of 
the  cones  of  Jjc/ndoph/oioM  nccords  with  Ihisconeiiision. 

The  species  of  Lppidophloios  are  numerous,  and  individuals  arc 
quite  abundant  in  the  eoid  formation,  esjicciiiiiy  toward  its  u[>p«r 
I>art.  TlicHr  llattened  bari<  is  frefjuent  in  the  coal-beds  and  their 
roofs,  airordiri}^  a  thin  hiycT  of  i)ure  <!oul,  wiiich  sometimes  shows  the 
peculiar  laminated  or  scaly  charact(!r  of  the  bark  when  other  charac- 
ters are  almost  (entirely  obliterated.  The  leaves  also  are  nearly  as 
abundant  as  those  of  ,Sif/tfl(iri(i  in  tin;  coal-shales.  They  can  readily 
be  distin;^iiishe(l  by  tluiir  stronj,',  atij,'uliir  mid-rib. 

The  marUin;^s  of  Lcpi(lo])hl()ioH  may  e/isily  be  mistaken  for  those 
of  the  ('Ittt/irnrid  type*  of  SifjiUdria.  Whisn  th»!  stciui  only  is  seen, 
tli(\y  can  be  distin^juishcd  by  lh(!  len^jth  of  tlut  leaf-bases  in  Fjcpi- 
doph/oios,  tintl  by  tin;  dominatit  ceiitrul  vascular  scar ;  also  by  the 
one-nerv(!d  and  riblxid  leaves.  Wlu're  the  lar^o,  round  marks  of  the 
cones  are  pnisent,  these  are  an  infiillil)le  ^uide,  never  beiiif^  f)resent 
in  JSii/il/(iria.  As  1  he  cones  f^rew  on  the  u|»per  sides  of  I  he  branches, 
the  impiession  of  the  lower  side  often  shows  no  cotuj-scars,  or  ordy 
two  lateral  rows,  whereas  on  the  upi)er  side  of  th«!  same  branch  they 
aj)pear  s|»irally  arranj^ed.     I  may  dest;ribeus  an  exam|tle — 

fjcpidop/i/oioi  AcddidHUK,  Dawson.  Leaf-bases  broadly  rhom- 
bic, or  in  old  st(!ms  rej^ularly  rhoml)i(!,  prominent,  as(!(!ndin^',  termi- 
nated by  very  broad  rhombii;  scars  havinj^  a  central  point  and  two 
lateral  obscure  points.  Outt^r  bark  laminated  or  .scaly.  Surface  of 
inner  bark  with  sinj^le  points  or  depressions.  Leave?;  Ions',  linear, 
with  a  strouf?  keel  on  on(!  si<l(s  five  inches  or  more  in  lenj^th.  Cone- 
S(!ars  sparsely  scattered  on  tliick  branches,  either  in  two  rows  or 
spirally,  both  modes  b(!ing  sometimes  seen  on  the  same  brancih. 
Scalariform  axis  scarcely  an  inch  in  diameter  in  a  stem  live  inches 
thick.  Fruit,  an  ovate  strobile  with  numerous  acutu  scahis  covering 
small  globular  spfin^-cases.  This  spcci(;s  is  closely  allied  to  Uloden- 
drnn  majuti  and  LcpidopldoioH  faricmuH,  and  presents  numerous 
varieties  of  marking.     Coal-fonnation,  Nova  Scotia.        ,: 

Family  Calamitk.k  ;  (hmiH  Catamites,  Suckow. 

The  {)lants  of  this  genus  are  unrpiestionably  allied  to  the  mod- 
ern EquiHatacec,  but  excel  these  so  much  in  variety  of  form  and 
structure,  and  are  so  (.'apricious  in  their  states  of  preservation,  and  so 
liable  to  be  mistaken  f(jr  parts  of  plants  generically  different,  that 
they  have  given  rise  to  much  controversy.  The  following  considera- 
tions will  enable  us  to  arrive  at  some  certainty. 

The  genus  Calamites  was  originally   founded  in  the  longitu- 


itii  I 
iti  1 


THE  CARDONIFEROUS  FLORA. 


107 


dinally  riMtcd  und  jointed  stoms  so  frcr|iient  in  tho  eoal-fommtion, 
and  of  which  tlic  coinrnon  ('.  Suckorii  is  a  tyiticiil  form.  'I'hc  most 
perfoct  of  these  stfiiiH  n-preseiit  the  outer  siirfjice  iinniediateiy  witliin 
the  epiflerinis,  in  which  case  transvor«o  lines  or  constrietions 
mark  the  nodes,  anrl  at  tho  nodes  there  are  ronnded  spots,  some- 
times indi(!(ilin;^  nidiiil  processes  of  the  i)ith,  first  dcst^ribed  by 
Williamson  ;  in  other  cases,  the  attachment  of  hranchlels,  or  in  some 
specimens  both.  Hut  some  specimens  show  the  outer  surface  of  tho 
opirlermis,  in  which  case  tho  transverse  nodal  lines  are  usually  in- 
visible, tliou^^h  the  scars  f)f  brurichlets  may  appear.  Iti  still  other 
examples  the  whole  of  the  outer  tissu(!S  have  perished,  and  the  so- 
cailetl  Calamite  is  a  cast  of  the  interior  of  the  stem,  showing  merely 
longitudinal  ribi>inj,'  and  transverse  nodal  constrictions.  In  study- 
ing' these  plants  in  m'tu  in  the  erect  Calamite  brakes  of  the  coal- 
foririation  of  Nova  Scotia,  one  soon  becomes  familiar  with  these  ap- 
pearances, but  th(!y  are  evidently  unknown  to  the  majority  of  palajo- 
botanists,  though  described  in  detail  more  than  twenty  years  ago. 

When  th(!  outer  surfa(;e  is  preserved  it  is  sometinu's  seen  to  bear 
vcrti(;ils  of  iutig  nee(ll(!-lik(!  leaves  (C.  (Jift/ii),  or  of  branchlets  with 
secondary  whorls  of  similar  leaves  {(J.  Suclcovii  and  C.  rmdidatuH), 
No  ('alamito  known  to  mo  bears  broad  one-nerved  leaves  like  those 
of  Aiit''rop/n///i/t'fi  iiiul  Annuhirid,  though  the  larger  stems  of  these 
plants  have  been  described  as  Calauiitcs,  and  the  term  ('alftmoclatlus 
has  been  used  to  includt;  both  groups.  The  base  of  the  ('alamito 
stem  usually  tcrminat(!S  in  a  blunt  point,  and  may  be  attached  to  a 
rhizome,  or  sevc^ral  steins  may  bud  out  from  each  other  in  a  group  or 
stool.  Tho  roots  are  long  and  cylindrical,  sometimes  branching. 
The  fruit  consists  of  spikes  of  spore-cases,  borne  in  whorls  and  sub- 
t(!nded  by  linear  floral  leaves.  To  these  strobiles  tho  name  Calamo- 
stachys  has  been  given. 

Williamson  has  shown  that  the  stem  of  Calamitcs  consists  of  a 
central  pith  or  cavity  of  large  size  surroutided  by  a  cylinder  con- 
sisting of  alternato  wedges  ot  woody  and  cellular  matter,  with  ver- 
tical canals  at  the  iimer  sides  of  tlu;  wedges,  and  slender  medullary 
rays.  The  thick  cellular  wedges  intervening  between  the  woody 
wedges  he  calls  [irimary  medullary  rays;  the  smaller  medullary 
rays  in  the  wedges,  secondary  medullary  rays.  There  is  thus  a 
highly  complex  exogenous  stem  based  on  the  same  principle  with 
the  stem  of  a  common  Equiadum,  but  with  much  greater  strength 
and  complexity. 

Williamson  has  also  shown  that  there  are  different  sub-tyi)es  of 
these  stems.    More  especially  he  refers  to  the  three  following: 


108 


THE  (JEOLOfJICAL  IIISTonY  OF  PLANTS. 


i 


I 


!i 


inn  I 


I 


ii:- 

.:  ii 


Hr 


\-j 


(a)  Cnlamites  proper,  which  lias  tho  woody  wo<l(f«>s  of  soalari- 
form  or  Imrred  tiH.sii«  with  Uiin  nicduliiiry  ruyH,  and  the  thick  pri- 
mary incchillary  ruy.s  arc  c(;ihihir. 

(/i)  <'(U(imo])ilHH  hiin  reticulated  or  rniilliporouH  tJHsiio  in  tlio 
woody  wedges  with  medullary  rays,  and  tlic  primary  mciduilary 
wed^oH  are  (;omiK»8(!«l  <A  clonj;al(;d  c(«IIh. 

(c)  (Jalainodendrfm  has  tiie  woody  wodgcs  t)l  hjirrcd  tissue  as  in 
a,  with  medullary  rays,  hut  iias  the  interv(!iiirij^  medullary  wedt^es 
of  an  cU)n^atcd  tissue  approa<!liing  to  woody  film;,  and  also  with 
medullary  rays. 

To  these  I  would  add  a  fourth  type,  which  I  have  described,  from 
the  coal-formation  of  Nova  S<otia.* 

(d)  h'ucdfamodriidron  diirers  from  (Jalamodcndron  in  having 
true  bordered  pores  or  pseudo-scalariform  slit-pored  tissue,  and  cor- 
responds tr>  tho  highest  tyfw  of  calamitean  stem. 

F  would  also  add  that  under  a  and  h  there  are  some  species  in 
which  the  woody  cylinder  is  very  thin  in  com[)arison  to  the  size  of 
the  stem.  In  c  and  d  the  woody  cylinder  is  thick  and  massive,  and 
the  stems  are  often  large  and  nodose. 

As  an  example  of  an  ordinary  C'alamite  in  which  the  external 
surface  and  foliat,'e  arc  [)reservcd,  I  iruiy  (piotc  the  following  from 
my  report  on  the  "  l''l(jra  of  the  Jjower  Carboniferous  antl  Millstone 
Grit,"  1H7:{: 

Calamitks  IT.vniiLATUs,  Brongniart. — This  species  is  stated  by 
Brongniart  to  ))e  distinguished  from  Ww  ('.  Snr.lcovii,  the  character- 
istic ('alamite  of  the  middle  coal-formation,  by  its  undulated  ribs 
marked  with  fieculiar  cellular  reticulation.  He  suggests  that  it  may 
be  merely  a  varirdy  of  6'.  Sur.kovii,  an  opinion  in  which  Schimper 
coincides;  ])ut  since  I  have  received  large  additif)nal  collections  from 
Mr.  Elder,  containing  not  only  the  stems  and  branches,  but  also  tho 
leaves  and  rhizomes,  I  am  constrained  to  regard  it  as  a  distinct 
thougli  closely  allied  species. 

The  rhizomata  anf  slender,  being  from  one  to  two  inches  in 
diameter,  and  jierftfctly  flattencid.  'i'hey  an:  beautifully  covered  with 
u  cellular  niticulation  on  tlu;  thin  Imrk,  and  shf)W  occasiomil  round 
areoles  marking  the  points  of  (ixit  of  the  rootlets.  I  have  long  Ijeen 
familiar  with  irregular  flattened  st(!ms  thus  reticulate,  ))ut  have  only 
recently  been  able  to  connect  them  with  this  species  of  C'alamite. 

The  nuiin  stems  present  a  very  thin  carlKiiiateous  bark  reticu- 
lated like  th(!  rhizomes.     They  hav(!  flat,  broad  ribs  sej)arated  by  deep 

*"  Quarterly  Journal  of  the  Geological  Society,"  1871. 


THE  CARUOXIFKIiOUS  FLORA. 


109 


and  narrow  furrows  and  utKluliitcd  in  a  rcmarkahln  mannfr  oven 
when  lilt'  HtciiiHure  Jliitt«'iH'<l.  Tliis  iniil  illation  is,  liowcvcr.  iMi'liapsim 
itifJication  of  vcrliuil  pn-ssurti  while  the  plant  w»ih  living,  a-^  it  secfrns 
to  huvo  hwl  an  unii.siially  thin  and  fceblo  rortical  layer,  and  the  im- 
dulation.s  are  ap|mreiitly  Ix-.st  developed  in  the  lowtrr  f)art  of  the  stem. 
At  the  nodes  the  ril)s  are  often  narrowed  and  ^utliered  to^'eiher, 
cspocially  in  the  vieinity  of  the  roiinde<|  radiating  niark.s  whieli  ap- 
jiear  to  indi(.'at(!  the  jjointH  of  inwirtion  of  the  branches.  At  th(!  top 
of  each  rih  we  have  the  usual  rounded  aroole,  probably  tnarkin;;  the 
insertion  of  a  primary  branchlet. 

The  braniln-s  liave  slender  ribs  and  distal  t  nodes,  from  whieh 
Hpriiiff  secondary  branchlets  in  whorls,  these  bearing  in  turn  small 
whorls  of  acMcular  lealhits  nnieh  curvcid  upward,  and  which  are  ap- 
parently round  in  entss  section  aii<l  delicately  striate.  'J'hey  aro 
much  shorter  than  tlii;  leav(;s  of  ('(iltunili-»  Suckovii,  iind  aro  less 
dense  and  less  curved  than  those  of  C.  nodosKs,  which  I  iKrlievc  lobe 
the  two  moHi  closely  ullied  sjjocies. 

Les(piercux  notices  this  s|)eci»;s  asr-haractoristic  of  the  lower  part 
of  the  Carboniferous  in  Arkansas. 

It  will  be  observed  that  I  regard  the  striated  and  ribbed  stems  not 
as  internal  axes,  but  as  representing  the  outer  surface  of  the  [ilants. 
This  was  certainly  the  (tase  with  the  f)resent  sjiecies  and  with  C. 
iSur/iovii  and  ( '.  hoi/ohuh.  Other  speci(!s,  and  espe<'ially  thos<!  which 
belonged  to  ("alamodendron,  no  d(jubt  had  a  smooth  or  irregularly 
wrinkltMl  external  bark;  but  this  gives  no  good  ground  for  the  man- 
ner in  which  some  writers  on  this  subje(;t  cfti.'found  ('alainites  with 
Calamodendra,  and  both  with  Asterophyllit(!S  and  Spheiiophylliim. 
With  this  no  one  who  has  studi(;d  thes<'  plants,  r(M)ted  in  their  native 
soils,  and  with  their  appendages  still  attached,  can  for  u  moment 
sympathise.  One  of  the  earliest  geological  studies  of  the  writer  was 
a  bed  of  these  erect  Calamites,  which  h(!  showed  to  Sir  ('.  Lyell  in 
1H44,  and  described  in  the  "  I'roeecidings  of  th(i  (ieologi(;al  Socictty" 
in  1851,  illustrating  the  habit  of  growth  as  actually  seen  well  ex- 
posed in  a  sandstone  cliff.  Abundant  opportunities  (jf  verifying 
the  conclusions  formed  at  that  tiimt  have  since  occurred,  the  results 
of  wlii<'h  have  b(;en  summed  up  in  the  figures  in  Acadian  (jc<jlr>gy, 
which,  though  they  have  Ixien  treated  by  some  Ijotanists  as  merely 
restorations,  are  in  reality  rej)resetilations  of  facts  a<;tiially  observed. 

On  these  subjects,  without  entering  into  details,  and  referring 
for  these  to  the  elaliorate  discussions  of  Schimpcr,  Williamson,  and 
McXab,  and  to  my  paper  on  the  subject,  "  Journal  of  the  Geological 
Society,"  vol.  xxvii,  p.  54,  I  may  remark  : 


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23  WEST  MAIN  STREET 

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170 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


:!|       i-i 


S   I 


i^u  - ! ; 


1.  That  the  aerial  stems  of  ordinary  Calamites  had  a  thin  cortical 
layer,  with  lacunae  and  fibrous  bundles  and  multiporous  vessels — the 
whole  not  differing  much  from  the  structure  of  modern  Equiscta. 

2.  Certain  arborescent  forms,  perhaps  allied  to  the  true  Calamites, 
as  well  as  possibly  the  old  underground  stems  of  ordinary  species,* 
assumed  a  thick-walled  character  in  which  the  tissues  resembled  the 
wedges  of  an  exogen,  and  abundance  of  pseudo-scalariform  fibres  were 
developed,  while  the  ribbitig  of  the  external  surface  became  obsolete 
or  was  replaced  by  a  mere  irregular  wrinkling.  -  '._-'■ 

3.  Sufficient  discrimination  has  not  been  exercised  in  separating 
casts  of  the  internal  cavities  of  Calamites  and  Calamodendron  from 
those  representing  other  surfaces  and  the  proper  external  surface. 

4.  There  is  no  excuse  for  attributing  to  Calamites  the  foliage  of 
Annularia,  Asterophyllites,  and  Sphenophyllum,  since  these  leaves 
have  not  been  found  attached  to  true  Calamite  stems,  and  since  the 
structure  of  the  stems  of  Asterophyllites  as  described  by  Williamson, 
and  that  of  Sphenophyllum  as  described  by  the  writer,f  are  essen- 
tially different  from  those  of  Calamites. 

5.  As  the  species  above  described  indicates,  good  external  char- 
acters can  be  found  for  establishing  species  of  this  genus,  and  these 
species  are  of  value  as  marks  of  geological  age.  ' ' 

Genus  Arch.^ocalamites,  Sternberg. 

Tills  genus  has  been  established  to  include  certain  Calamites  of 
the  Devonian  ai.'l  Lower  Carboniferous,  in  which  the  furrows  on  the 
stem  do  not  alteri  ate  at  the  nodes  or  joints,  and  the  leaves  in  one 
species  at  least  bifurcate.  C.  radiatus,  Brongniart,  is  the  typical 
species.  In  North  America  it  occurs  in  the  Erian,  probably  as  low 
as  the  Middle  Erian.  In  Europe  it  has  so  far  been  recognised  in  the 
Lower  Carboniferous  only.  I  have,  however,  seen  stems  from  alleged 
Devonian  beds  in  Devonshire  which  may  have  belonged  to  this  species. 

Family  AsTEROPiiYLLiTEiE;    Oenus  Asterophyllites,  Brongniart. 

Stems  ribbed  and  jointed  like  the  Calamites,  but  with  inflated 
nodes  and  a  stout  internal  woody  cylinder,  which  has  been  described 
by  Williamson.  From  the  joints  proceeded  whorls  of  leaves  or  of 
branchlets,  bearing  leaves  which  differed  from  those  of  Calamites  in 
their  having  a  distinct  middle  rib  or  vein.     The  fructification  con- 


*  Williamson,  "  Transactions   of    the   Royal   Society." 
"Proceedings  of  the  Edinburgh  Botanical  Society." 
f  "Journal  of  the  Geological  Society,"  1866. 


McNab,   in 


THE  CARBONIFEROUS  FLORA. 


171 


sisted  of  long  slender  cones  or  spikes,  having  whorls  of  scales  bear- 
ing the  sporo-cases.  Some  authors  speak  of  AsterophyUitea  as  only 
branches  ai  1  leaves  of  Calamites;  but  though  at  first  sight  the  re- 
semblance is  great,  a  close  inspection  shows  that  the  leaves  of  As- 
terophyllites  have  a  true  midrib,  which  is  wanting  in  Calamites. 

Genus  Annularia. — It  is  perhaps  questionable  whether  these 
plants  should  be  separated  from  AsterophyUifes.  The  distinction  is 
that  they  produce  branches  in  pairs,  and  that  their  whorls  of  leaves 
are  one-sided  and  usually  broader  than  those  of  AsterophyUifes,  and 
united  into  a  ring  at  their  insertion  on  the  stem.  One  little  speciea, 
A.  sphenophylloides,  is  very  widely  distributed. 

PiNNULARiA — a  provisional  genus — includes  slender  roots  or  stems 
branching  in  a  pinnate  manner,  and  somewhat  irregularly.  They 
are  very  abundant  in  the  coal  shales,  and  were  probably  not  inde- 
pendent plants,  but  aquatic  roots  belonging  to  some  of  the  plants 
last  mentioned.  The  probability  of  this  is  farther  increased  by  their 
resemblance  in  miniature  to  the  roots  of  Calamites,  They  are  always 
flattened,  but  seem  originally  to  have  been  round,  with  a  slender 
thread-like  axis  of  scalariform  vessels,  enclosed  in  a  soft,  smooth, 
cellular  bark. 

Family  Rihzocarpe^^  ;  Genus  Sphenopiiyllum.         .    i 

Leaves  in  whorls,  wedge-shaped,  with  forking  veins.  Fructi- 
fication on  spikes,  with  verticils  of  sporocarps.  These  plants  are 
by  some  regarded  as  allied  to  the  Calamifem  and  Asterophyllitece,  by 
others  as  a  high  grade  of  Rhizocarps  of  the  type  of  Marsilia.  The 
stem  had  a  star-shaped  central  bundle  of  scalariform  or  reticulato- 
scalariform  vessels. 


:  Genus  SpoRAyaiTES.    (Sporocarpon,  VliUiamson.) 

Under  this  name  we  may  provisionally  include  those  rounded 
spherical  bodies  found  in  the  coal  and  its  accompanying  beds,  and 
also  in  the  Eriiin,  which  may  be  regarded  as  IMacrospores  or  Sporo- 
carps of  Protosr-Vinia,  or  other  Khizocarpean  plantsakin  to  those  de- 
scribed above  in  Chapter  III,  which  see  for  description. 

Genus  Protosalvinia. — Under  this  we  include  sporocarps  allied 
to  those  of  Salvinia,  as  described  in  Chapter  III. 

Family  FiucES. 

Under  this  head  I  shall  merely  refer  to  a  few  groups  of  special 
interest,  and  to  the  provisional  arrangement  adopted  for  the  fronds 
of  ferns  when  destitute  of  fructification. 


172 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


Ivl 


U 


The  external  appearances  of  trunks  of  tree-ferns  have  been  al- 
ready referred  to. 

With  respect  to  tree  ferns,  the  oldest  known  examf)]es  are  those 
from  the  Middle  Devonian  of  New  York  and  Ohio,  which  I  have  de- 
scribed in  the  "Journal  of  the  Geological  Society,"  1871  and  1881. 
As  these  are  of  some  interest,  I  have  reproduced  their  descriptions 
in  a  note  appended  to  Chapter  III,  which  see. 

The  other  forms  most  frequently  occurring  in  the  Carboniferous 
are  Caulopteris,  Palceopferis,  and  Megaphyton.*  Stems  showing 
merely  masses  of  aerial  roots  are  known  by  the  name  Psaronius. 

With  reference  to  the  classification  of  Palaeozoic  ferns,  this  has 
hitherto  been  quite  arbitrary,  being  based  on  mere  form  and  vena- 
tion of  fronds,  but  much  advance  has  recently  been  made  in  the 
knowledge  of  their  fructification,  warranting  a  more  definite  at- 
tempt at  classification.  The  following  are  provisional  genera  usu- 
ally adopted : 

1.  Cydopteris,  Brongniart. — Leaflets  more  or  less  rounded  or 
wedge-shaped,  without  midrib,  the  nerves  spreading  from  the  point 
of  attachment.  This  group  includes  a  great  variety  of  fronds  evi- 
dently of  diilerent  genera,  were  their  fructification  known  ;  and  some 
of  them  probably  portions  of  fronds,  the  other  parts  of  which  may 
be  in  the  next  genus. 

2.  Neuropteris,  Brongniart. — Fronds  pinnate,  and  with  the 
leaflets  narrowed  at  the  base ;  midrib  often  not  distinct,  and  disap- 
pearing toward  the  apex.  Nervures  equal,  and  rising  at  an  acute 
angle.  Ferns  of  this  type  are  among  the  most  abundant  in  the  coal- 
formation. 

3.  Odontopteris,  Brong.  'art. — In  these  :he  frond  is  pinnate,  and 
the  leaflets  are  attached  by  their  whole  base,  with  the  nerves  either 
proceeding  wholly  from  the  base,  or  in  part  from  an  indistinct  mid- 
rib, which  soon  divides  into  nervures. 

4.  Dictyopteris,  Gutbier. — This  is  a  beautiful  style  of  fern,  with 
leaflets  resembling  those  of  Neuropteris,  but  the  veins  arranged  in  a 
network  of  oval  spaces.  Only  a  few  species  are  known  in  the  coal- 
formation. 

5.  Lonchopteris,  Brongniart. — Ferns  with  netted  veins  like  the 
above,  but  with  a  distinct  midrib,  and  the  leaflets  attached  by  the 
whole  base.     Of  this,  also,  we  can  boast  but  few  species. 

6.  Sphenopteris,  Brongniart. — These  are  elegant  ferns,  very  nu- 
merous in  species,  and  most  difficult  to  discriminate.    Their  mos'i 


*  See  my  "  Acadian  Geology,"  also  below. 


THE  CARBONIFEROUS  FLORA. 


173 


distinctive  characters  are  leaflets  narrowed  at  the  base,  often  lobed, 
and  with  nervures  dividing  in  a  pinnate  manner  from  the  base. 

7.  Fhyllopteris,  Brongniart. — These  are  pinnate,  with  long  lan- 
ceolate pinnules,  having  a  strong  and  well-defined  midrib,  and 
nerves  proceeding  from  it  very  obliquely,  and  dividing  as  they  pro- 
ceed toward  the  margin.  The  ferns  of  this  genus  are  for  the  most 
part  found  in  formations  more  recent  than  the  Carboniferous ;  but  I 
have  referred  to  it,  with  some  doubt,  one  of  our  species. 

8.  Alethopteris,  Brongniart. — This  genus  includes  many  of  the 
most  common  coal-formation  ferns,  especially  the  ubiquitous  A.  lon- 
chifica,  which  seems  to  have  been  the  common  brake  of  the  coal- 
formation,  corresponding  to  Pteris  aquilina  in  modern  Europe  and 
America.  These  are  brake-like  ferns,  pinnate,  with  leaflets  often 
long  and  narrow,  decurrent  on  the  petiole,  adherent  by  their  whole 
base,  and  united  at  base  to  each  other.  The  midrib  is  continuous  to 
the  point,  and  the  nervures  run  off  from  it  nearly  at  right  angles. 
In  some  of  these  ferns  the  fructification  is  known  to  have  been  mar- 
ginal, as  in  Pteris. 

9.  Pecopteris,  Brongniart. — This  genus  is  intermediate  between 
the  last  and  Neuropteris.  The  leaflets  are  attached  by  the  whole 
base,  but  not  usually  attached  to  each  other;  the  midrib,  though 
slender,  attains  to  the  summit;  the  nervures  are  given  off  less  ob- 
liquely than  in  JSeuropteris.  This  genus  includes  a  large  number  of 
our  most  common  fossil  ferns. 

10.  Beinertia,  Goeppert. — A  genus  established  by  Goeppert  for  a 
curious  Pecopteiis-liko  fern,  with  flexuous  branching  oblique  ner- 
vures becoming  parallel  to  the  edge  of  the  frond. 

11.  Hymenophyllites,  Goeppert. — These  are  ferns  similar  to 
Sphenopteris,  but  divided  at  the  margin  into  one-nerved  lobes,  in  the 
manner  of  the  modern  genus  HymenophyUum, 

12.  Palffopferis,  Geinitz. — This  is  a  genus  formed  to  mclude  cer- 
tain trunks  of  tree-ferns  with  oval  transverse  scars  of  leaves. 

13.  Cnulopferis,  Lindley  and  Hutton. — Is  another  genus  of  fossil 
trunks  of  tree-ferns,  but  with  elongate  scars  of  loaves. 

14.  Psaronins,  Cotta. — Includes  other  trunks  of  tree-ferns  with 
alternate  scars  or  thick  scales,  and  ordinarily  with  many  aerial  roots 
grouped  round  them,  as  in  some  modern  tree-ferns. 

15.  Megaphyton,  Artis. — Includes  trunks  of  tree-ferns  which 
bore  their  fronds,  which  were  of  great  size,  in  two  rows,  one  on  each 
side  of  the  stem.  These  were  very  peculiar  trees,  less  like  modern 
ferns  than  any  of  the  others.  My  reasons  for  regarding  thera  as 
ferns  are  stated  in  the  following  extract  from  a  recent  paper : 


174 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


Ii1!'-^ 


"Their  thick  stems,  marked  nith  linear  scars  and  having  two 
rows  of  large  depressed  areoles  on  the  sides,  suggest  no  affinities  to 
any  known  plants.  They  are  usually  ranked  with  Lepidodendron 
and  Ulodendron,  but  sometimes,  and  probably  with  greater  reason, 
are  regarded  as  allied  to  tree-ferns.  At  the  Joggins  a  very  fine 
species  (Jf.  magnificum)  has  been  found,  and  at  Sydney  a  smaller 
species  (M.  humile)  ;  but  both  are  rare  and  not  well  preserved.  If 
the  large  scars  bore  cones  and  the  smaller  bore  leaves,  then,  as  Bron- 
gniart  remarks,  the  plant  would  much  resemble  Lepidophloios,  in 
which  the  cone-scars  are  thus  sometimes  distichous.  But  the  scars 
are  not  round  and  marked  with  radiating  scales  as  in  Lepidophloios; 
they  are  reniform  or  oval,  and  resemble  those  of  tree-ferns,  for  which 
reason  they  may  bo  regarded  as  more  probably  leaf-scars ;  and  in 
that  case  the  smaller  linear  scars  would  indicate  ramenta,  or  small 
aerial  roots.  Further,  the  plant  described  by  Corda  as  Zippea  die- 
ticha  is  evidently  a  Megaphyton,  and  the  structure  of  that  species  is 
plainly  that  of  a  tree-fern  of  somewhat  peculiar  type.  On  these 
grounds  I  incline  to  the  opinion  of  Geinitz  that  these  curious  trees 
were  allied  to  ferns,  and  bore  two  rows  of  large  fronds,  the  trunks 
being  covered  with  coarse  hairs  or  small  aerial  roots.  At  one  time  I 
was  disposed  to  suspect  that  they  may  have  crept  along  the  ground ; 
but  a  specimen  from  Sydney  shows  the  leaf-stalks  proceeding  from 
the  stem  at  an  angle  so  acute  that  the  stem  must,  I  think,  have  been 
erect.  From  the  appearance  of  the  scars  it  is  probable  that  only  a 
pair  of  fronds  were  borne  at  one  time  at  the  top  of  the  stem ;  and,  if 
these  were  broad  and  spreading,  it  would  be  a  very  graceful  plant. 
To  what  extent  plants  of  this  type  contributed  to  the  accumulation 
of  coal  I  have  no  means  of  ascertaining,  their  tissues  in  the  state  of 
coal  not  being  distinguishable  from  those  of  ferns  and  Lyco- 
podiacecey 

•    16.  For  descriptions  of  the  genus  Archmopteris  and  other  Erian 
ferns,  see  Chapter  III.  ,. 


:i.  i 


wa  j-j 


CHAPTER  V. 


,i^i 


THE   FLORA   OF  THE  EARLY   MESOZOIC. 


Great  physical  changes  occurred  at  the  close  of  the 
Carboniferous  age.  The  thick  beds  of  sediment  that  had 
been  accumulating  in  long  lines  along  the  primitive  con- 
tinents had  weighed  down  the  earth's  crust.  Slow  sub- 
sidence had  been  proceeding  from  this  cause  in  the  coal- 
formation  period,  and  at  its  close  vast  wrinklings  occurred, 
only  surpassed  by  those  of  the  old  Laurentian  time. 
Hence  in  the  Appalachian  region  of  America  we  have  the 
Carboniferous  heds  tiirown  into  abrupt  folds,  their  shales 
converted  into  hard  slates,  their  sandstones  into  quartzite 
and  their  coals  into  anthracite,  and  all  this  before  the 
deposition  of  the  Triassic  Red  Sandstones  which  consti- 
tute the  earliest  deposit  of  the  great  succeeding  Mesozoic 
period.  In  like  manner  the  coal  -  fields  of  Wales  and 
elsewhere  in  western  Europe  have  suffered  similar  treat- 
ment, and  apparently  at  the  same  time. 

This  folding  is,  however,  on  both  sides  of  the  Atlantic 
limited  to  a  band  on  the  margin  of  the  continents,  and  to 
certain  interior  lines  of  pressure,  while  in  the  middle,  as 
in  Ohio  and  Illinois  in  America,  and  in  the  great  interior 
plains  of  Europe,  the  coal-beds  are  undisturbed  and  un- 
altered. In  connection  with  this  we  have  an  entire 
change  in  the  physical  character  of  the  deposits,  a  great 
elevation  of  the  borders  of  the  continents,  and  probably 
a  considerable  deepening  of  the  seas,  leading  to  the  estab- 
lishment of  general  geographical  conditions  which  still 
remain,  though  they  have  been  temporarily  modified  by 
subsequent  subsidences  and  re-elevations. 


nif  M 


1    ■ 

^i!       i    '>i 

lilt  ! 

;    i 


170 


THE  GEOLOGICAL  HISTORY  OF  PLxVNTS. 


Along  with  this  a  great  cliange  was  in  progress  in 
vegetable  and  animal  life.  The  flora  and  fauna  of  the 
Paleozoic  gradually  die  out  in  the  Permian  and  are  re- 
placed in  the  succeeding  Trias  by  those  of  the  Mesozoic 
time.  Throughout  the  Permian,  however,  the  remains 
of  the  coal-formation  flora  continue  to  exist,  and  some 
forms,  as  the  Calamites,  even  seem  to  gain  in  importance, 
as  do  also  certain  types  of  coniferous  trees.  The  Triassic, 
as  well  as  the  Permian,  was  marked  by  i)hysical  disturb- 
ances, more  especially  by  great  volcanic  eruptions  dis- 
charging vast  beds  and  dykes  of  lava  and  layers  of  volcanic 
ash  and  agglomerate.  This  was  the  case  more  especially 
along  the  margins  of  the  Atlantic,  and  probably  also  on 
those  of  the  Pacific.  The  volcanic  sheets  and  dykes  as- 
sociated with  the  Red  Sandstones  of  Nova  Scotia,  Con- 
necticut, and  New  Jersey  are  evidences  of  this. 

At  the  close  of  the  Permian  and  beginning  of  the 
Trias,  in  the  midst  of  this  transition  time  of  physical 
disturbance,  appear  the  great  reptilian  forms  character- 
istic of  the  age  of  reptiles,  and  the  earliest  precursors  of 
the  mammals,  and  at  this  time  the  old  Carboniferous 
forms  of  plants  finally  pass  away,  to  be  replaced  by  a 
flora  scarcely  more  advanced,  though  different,  and  con- 
sisting of  pines,  cycads,  and  ferns,  with  gigantic  equiseta, 
which  are  the  successors  of  the  genus  Calamites,  a  genus 
which  still  survives  in  the  early  Trias.  Of  these  groups 
the  conifers,  the  ferns,  and  the  equiseta  are  already  famil- 
iar to  us,  and,  in  so  far  as  they  are  concerned,  a  botanist 
who  had  studied  the  flora  of  the  Carboniferous  would 
have  found  himself  at  home  in  the  succeeding  period. 
The  cycads  are  a  new  introduction.  The  whole,  how- 
ever, come  within  the  limits  of  the  cryptogams  and  the 
gymnosperms,  so  that  here  we  have  no  advance.* 

*  Fontaine's  "  Early  Mesozoic  Flora  of  Virginia  "  gives  a  very  good 
summary  of  this  flora  in  America,  ,      . 


1 


TliE  FLORA.  OF  THE   EARLY   MESOZOIC. 


177 


As  we  ascend,  Jiowever,  in  the  Mesozoic,  we  find  new 
and  higher  types.  Even  within  the  Jurassic  epoch,  the 
next  in  succession  to  the  Trias,  there  are  clear  indica- 
tions of  tlie  presence  of  the  cndogens,  in  species  allied  to 


Fia.  6-i. — Jurassic  vegetation.     Cycads  and  pines.     (After  Saporta.) 

the  screw-pines  and  grasses  ;  and  the  palms  appear  a 
little  later,  while  a  few  exogenous  trees  have  left  their 
remains  in  the  Lower  Cretaceous,  and  in  the  Middle  and 
Upper  Cretaceous  these  higher  plants  come  in  abund- 
antly and  in  generic  forms  still  extant,  so  that  the  dawn 
of  the  modern  flora  belongs  to  the  Middle  and  Upper 
17 


178 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


Cretaceous.  It  will  thus  be  convenient  to  confine  our- 
selves in  this  chapter  to  the  flora  of  the  earlier  Mesozoic. 
Passing  over  for  the  present  the  cryptogamous  plants 
already  familiar  in  older  deposits,  we  may  notice  the  new 
features  of  gymnospermous  and  phaenogamous  life,  as  they 
present  themselves  in  this  earlier  part  of  the  great  rep- 
tilian age,  and  as  they  extended  themselves  with  remark- 
able uniformity  in  this  period  over  all  parts  of  the  world. 
For  it  is  a  remarkable  fact  that,  if  we  place  together  in 
our  collections  fossil  plants  of  this  period  from  Australia, 
India,  China,  Siberia,  Europe,  or  even  from  Greenland, 
we  find  wonderfully  little  difference  in  their  aspect.  This 
uniformity  we  have  already  seen  prevailed  in  the  Palaeo- 
zoic flora ;  and  it  is  perhaps  equally  marked  in  that  of 
the  Mesozoic.  Still  we  must  bear  in  mind  that  some 
of  the  plants  of  these  joeriods,  as  the  ferns  and  pines, 

for  example,  are  still 
world  -  wide  in  their 
distribution ;  but  this 
does  not  apply  to  oth- 
ers, more  especially 
the  cycads  (Fig.  65). 
The  cycads  consti- 
tute a  singular  and  ex- 
^^^^^  ,  ceptional  type  in  the 

"^  ~"^  ^"^--v^       11      i/  modern    world,    and 

are  limited  at  present 
to  the  warmer  cli- 
mates, though  very 
generally  distributed 
in  these,  as  they  oc- 
cur in  Africa,  India, 
Japan,  Australia,  Mexico,  Florida,  and  the  West  Indies. 
In  the  Mesozoic  age,  however,  they  were  world-wide  in 
their  distribution,  and  are  found  as  far  north  as  Green- 
land, though  most  of  the  species  found  in  the  Cretaceous 


Fig.  65, — Podozamites  lanceolatus,  Stcrab. 
L.  Cretaceous. 


THE  FLOliA  OP  THE  EARLY   MESOZOIC. 


179 


of  that  country  are  of  small  size,  and  may  have  been  of 
low  growth,  80  that  tliey  may  have  been  protected  by  the 
snows  of  winter.  The  cycads  have  usually  simple  or  un- 
branching  stems,  pinnate  leaves  borne  in  a  crown  at  top, 
and  fruits  which,  though  somewhat  various  in  structure 
and  arrangement,  are  all  of  the  sim})ler  form  of  gymno  ■ 
spermous  type.  The  stems  are  exogenous  in  structure, 
but  with  slender  wood  and  thick  bark,  and  barred  tissue, 
or  properly  as  tissue  intermediate  between  this  and  the 
disc-bearing  fibres  of  the  pines. 

Though  the  cycads  have  a  considerable  range  of  or- 
ganisation and  of  fructification,  and  though  some  points 
in  reference  to  the  latter  might  assign  them  a  higher 
place,  on  the  whole  they  seem  to  occupy  a  lower  position 
than  the  conifers  or  the  cordaitcfe  of  the  Carboniferous. 
In  the  Carboniferous  some  of  the  fern-like  leaves  assigned 
to  the  genus  Noefjgerathia  have  been  shown  by  Stur  and 
Weiss  to  have  been  gymnosperms,  probably  allied  to 
cycads,  of  which  they  may  be  regarded  at  least  as  pre- 
cursors. Thus  the  cycadean  type  does  not  really  consti- 
tute an  advance  in  grade  of  organisation  in  the  Mesozoic, 
any  further  than  that,  in  the  period  now  in  question,  it 
becomes  much  more  developed  in  number  and  variety  of 
forms.  But  the  conifers  would  seem  to  have  had  preced- 
ence of  it  for  a  long  time  in  the  Palajozoic,  and  it  replaces 
in  the  Mesozoic  the  Cordaites,  which  in  many  respects 
excelled  it  in  complexitj^ 

The  greater  part  of  the  cycads  of  the  Mesozoic  age 
would  seem  to  have  had  short  stems  and  to  have  consti- 
tuted the  undergrowth  of  woods  in  which  conifers  at- 
tained to  greater  height.  An  interesting  case  of  this  is 
the  celebrated  dirt-bed  of  the  quarries  of  the  Isle  of  Port- 
land, long  ago  described  by  Dean  Buckland.  In  this 
fossil  soil  trunks  of  pines,  which  must  have  attained  to 
great  height,  are  interspersed  with  the  short,  thick  stems 
of  cycads,  of  the  genus  named  Cycadoidea  by  Buckland, 


r!_Li. 


M. 


i\ 


hi 

'■V  »  ' 


'ir  " 


si! 


M 


180 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


and  which  from  their  appearance  ai-e  called  "fossil 
birds'  nests ''  by  the  quarry  men.  Some,  however,  must 
have  attained  a  considerable  height  so  as  to  resemble 
palms. 

The  cycads,  with  their  simple,  thick  trunks,  usually 
marked  with  rhombic  scars,  and  bearing  broad  spreading 
crowns  of  large,  elegantly  formed  pinnate  loaves,  must 
have  formed  a  prominent  part  of  the  vegetation  of  the 
northern  hemis])here  during  the  whole  of  the  Mesozoic 
period.  A  botanist,  had  there  been  such  a  person  at  the 
time,  would  have  found  this  to  be  the  case  everywhere 
from  the  equator  to  Spitzbcrgen,  and  probably  in  the 
southern  hemisphere  as  well,  and  this  throughout  all  the 
long  periods  from  the  Early  Trias  to  the  Mit  'le  Cre- 
taceous. In  a  ^.aper  published  in  the  **  Linua?ai  Trans- 
actions" for  1808,  Dr.  Carruthers  enumerates  twenty  spe- 
cies of  British  Mesozoic  cycads,  and  the  number  might 
now  be  considerably  increased. 

The  pines  present  some  features  of  interest.  We  have 
already  seen  ti;eir  connection  with  the  broad-leaved  Cor- 
daites,  and  in  the  Permian  there  are  some  additional 

types  of  broad -leaved  coniferce. 
In  the  Mesozoic  we  have  great 
numbers  of  beautiful  trees, 
with  those  elegant  fan-shaped 
leaves  characteristic  of  but  one 
living  species,  the  Salisburia, 
or  gingko-tree  of  China.  It  is 
curious  that  this  tree,  though 
now  limited  to  eastern  Asia, 
will  grow,  though  it  rarely 
fruits,  in  most  parts  of  tem- 
perate Europe,  and  in  America  as  far  north  as  Montreal, 
and  that  in  the  Mesozoic  period  it  occupied  all  these  re- 
gions, and  even  Siberia  and  Greenland,  and  with  many 
and  diversified  species  (Fig.  6G). 


Fio.  66. — Salisburia  (Gingko) 
ISihirica.  Ileer.  L.  C'lvta- 
ceouti,  Siboria  and  North 
America. 


THE  FLORA  OF  THE  EARLY   MEriOZOIC. 


181 


Salisburia  belongs  to  the  yews,  but  an  equally  curious 
fact  applies  to  the  cypresses.  The  genus  Sequoia,  limited 
at  present  to  two  species,  both  Californian,  and  one  of 
them  the  so-called  **big  tree,"  celebrated  for  the  gigantic 
size  to  which  it  attains,  is  represented  by  species  found  as 
far  back  at  least  as  the  Lower  Cretaceous,  and  in  every 
part  of  the  northern  hemi- 
sphere.* It  seems  to  have 
thriven  in  all  these  regions 
throughout  tiie  Mesozoic 
and  early  Kainozoic,  and 
then  to  have  disappeared, 
leaving  only  a  small  rem- 
nant to  represent  it  in 
modern  days.  A  number 
of  species  have  been  de- 
scribed from  the  Mesozoic 
and  Tertiary,  all  of  them 
closely  related  to  those  now 
existing  (Fig.  G7). 

The  following  notice  of 
these  trees  is  for  the  most 
part  translated,  with  some 
modifications  and  abridg- 
ment, from  a  paper  read 
by  the  late  Prof.  Heer  be- 
fore the  Botanical  Section 
of  the  Swiss  Natural  His- 
tory Society : 

The  name  itself  deserves 
consideration.     It  is  that 

of  an  Indian  of  the  Cherokee  tribe,  Sequo  Yah,  who  in- 
ven'  .m  alphabet  without  ar.y  aid  from  the  outside  world 
of  culture,  and  taught  it  to  his  tribe  by  writing  it  upon 


Fic.  07.- 


-Sequoia  Smithiana,  Heer. 
L.  Cretaceous. 


*  In  the  Eocene  of  Australia. 


182 


THE   UKOLOGICAL   IIISTOUY  OF  PLANTS. 


loaves.  'IMiis  ciune  into  goneriil  use  among  tlio  Chcro- 
kcos,  before  the  white  man  had  any  knowlo(l<jfc  of  it ;  and 
nftorwanl,  in  1828,  a  ])erio(lieal  was  published  in  this 
eharaeter  by  the  missionaries.  Se(|uo  Yah  was  banished 
from  his  home  in  Ahibama,  with  the  rest  of  liis  tribe,  and 
settled  in  New  Mexieo,  where  he  died  in  184IJ. 

AVhen  Kndlieher  was  preparin*^  his  synopsis  of  the 
conifers,  in  1840,  and  liad  established  a  number  of  new 
genera,  Dr.  Jaelxm  'rseinidi,  then  livinj^  with  Eiullieher, 
brouglit  before  his  notice  this  remarkuble  man,  and  asked 
liim  to  dedicate  tliis  red-wooded  tree  to  the  memory  of  a 
literary  genius  so  conspicuous  among  the  red  men  of 
America.  Endiicher  consented  to  do  so,  and  only  en- 
deavored to  nuike  the  name  pronounceable  by  changing 
two  of  its  letlers. 

Eiullieher  founded  the  genus  on  the  redwood  of  the 
Americans,  Tttxodinin.  svmpcrvirenf^  oi  Land);  aiul  nanuMl 
the  s[)ecies  Sequoia  scmpcrvirctis.  'J'hese  trees  form  largo 
forests  in  California,  which  extend  alo!ig  the  coast  as  far 
as  Oregon.  Trees  are  there  met  with  of  liOO  feet  in  height 
and  JJO  feet  in  diameter.  The  seeds  have  been  brought 
to  Europe  a  number  of  years  ago,  and  we  already  see  iu 
upper  Italy  and  around  the  liake  of  (Jeneva,  and  in  Eng- 
land, high  trees  ;  but,  on  the  other  haiul,  they  iuivo  not 
proved  successful  arouiul  Zurich. 

In  I8r)5i,  a  second  species  of  Se(pu)ia  was  discovered  in 
California,  which,  under  the  name  of  big  tree,  soon  at- 
taiiu'd  a  considerable  celebrity.  Limlley  described  it,  in 
185.'J,  as  WvUiiKifonia  (/ii/dufcn  :  and,  in  the  following 
year,  Decaisne  and  Torrey  proved  that  it  belonged  to 
Sequoia,  and  that  it  iiccordingly  should  be  called  Sequoia 
(/it/an  tea. 

While  the  Sequoia  sempervirens,  in  spite  of  the  de- 
struetiveness  of  the  AnuM'iean  hunbermen,  still  forms 
large  fori'sts  along  the  coast,  the  Sequoia  (/iqanfea  is  con- 
lined  to  the  isolated  clumps  which  are  met  with  inland  ut 


1    H 


THE  FLORA  OF  THE  EARLY   MESOZOIC. 


183 


a  boij^ht  of  5,000  to  7,000  feet  above  scu-lovol,  and  are 
much  S()U}j^ht  after  by  tourists  as  one  of  the  wonders  of 
the  country.  l{e|)orts  came  to  Europe  coneernin<j;  tho 
larfi;est  of  them  wliieh  were  ((uite  fabuh>UH,  but  we  have 
received  accurate  accounts  of  them  from  Prof.  Whitney. 
Tho  tallest  tree  measured  by  him  has  a  hei^dit  of  '^25 
feet,  and  in  tho  case  of  one  of  the  trees  the  number  of  tho 
ring's  of  <,'rowth  indicated  an  age  of  about  1,300  years. 
Jt  had  a  <,'irth  of  60  to  00  feet. 

We  know  only  two  livini,'  spreies  of  Sequoia,  both  of 
which  arc^  conlined  to  California.  The  oiu'  (*S'.  seniprr' 
virvns)  is  (-lolhed  with  erect  leaves,  arran<jjed  in  two  rows, 
very  much  like  our  yew-tree,  and  bears  snnill,  round 
cones  ;  the  other  (*S'.  (/it/dH/vd)  has  smaller  leaves,  set 
closely  af]jainst  the  branches,  ^ivin<r  the  tree  more  the  ap- 
l)earance  of  the  cypress.  The  cones  are  epg-sha])ed,  and 
much  lar<,a'r.  These  two  types  arc  therefore  sharply  de- 
lined. 

Both  of  these  trees  liave  an  interestiuf]:  history.  If  wo 
go  back  into  the  Tertiary,  this  same  genus  meets  us  witli 
a  long  array  of  species.  Two  of  these  species  (!orres[)otid 
to  those  living  at  ])resent :  the  S.  iMnt/sdorfu  to  the  S, 
Si nipervircns,  and  the  S.  Con ff sup  to  the  S.  f/ii/ftnica.* 
liut,  while  the  livirjg  species  are  confined  to  California,  in 
the  Tertiary  they  are  spread  over  several  (piarters  of  tho 
globe. 

Let  us  first  consider  the  Sequoia  Lamisdorfii.  This 
was  first  discovered  in  the  lignite  of  Wetterau,  and  was 
described  as  Taxitos  hifu/sdorjli.  lleer  f»)und  it  in  the 
up|u'r  Rhone  district,  and  there  lay  beside  the  twigs 
the  remains  of  a  cone,  which  showed  that  the  Ta.rites 
L(iH(/s(/orJii  of  Hrongniart  belonged  to  the  Californian 
genus  Sequoia  established  by  Endlieher.     lie  afterward 

*  S.  Cottttsia;  has  loaves  like  S.  gujautea^  and  coues  like  tlioso  of  H. 
snnpervirais. 


I 

i 

! 


: ' ' : 

l|  ': 

i  M '    : , 

1 

ill 


184 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


found  much  better  preseryed  cones,  together  with  seeds, 
along  with  the  plants  of  east  Greenland,  which  fully 
confirmed  the  determination.  At  Atanekerdluk  in 
Greenland  (about  70°  north  latitude)  this  tree  is  very 
common.  The  leaves,  and  also  the  flowers  and  numerous 
cones,  leave  no  doubt  that  it  stands  very  near  to  the 
modern  redwood.  It  differs  from  it,  however,  in  hav- 
ing a  much  larger  number  of  scales  in  the  cone.  The  tree 
is  also  found  in  Spitzbergen  at  nearly  78°  north  latitude, 
where  Nordenskiold  has  collected,  at  Cape  Lyell,  wonder- 
fully preserved  branches.  From  this  high  latitude  the 
species  can  be  followed  down  through  the  whole  of  Eu- 
rope as  far  as  the  middle  of  Italy  (at  Senegaglia,  Gulf  of 
Spezia).  In  Asia,  also,  we  can  follow  it  to  the  steppes 
of  Kirghisen,  to  Possiet,  and  to  the  coast  of  the  Sea  of 
Japan,  and  across  to  Alaska  and  Sitka.  It  is  recognized 
by  Mr.  Starkie  Gardner  as  one  of  the  species  found  in 
the  Eocene  of  Mull  in  the  Hebrides.*  It  is  thus  known 
in  Europe,  Asia,  and  America,  from  43°  to  78°  north 
latitude,  while  its  most  nearly  related  living  species,  per- 
haps even  descended  from  it,  is  now  confined  to  Cali- 
fornia. 

With  this  S.  Langsdorfii,  three  other  Tertiary  species 
are  nearly  related  {S.  brevifoUa,  Hr.,  S.  disticha,  Hr., 
and  >S^.  Nordenskioldi,  Hr.).  These  have  been  met  with  in 
Greenland  and  Spitzbergen,  and  one  of  them  has  lately 
been  found  in  the  United  States.  Three  other  species,  in 
addition  to  these,  have  been  described  by  Lesquereux, 
which  appear  to  belong  to  the  group  of  the  S.  Langsdorfii, 
viz.,  S.  longifoUa,  Lesq.,  S.  angtistifolia,  and  S.  acu- 
minata, Lesq.  Several  species  also  occur  in  the  Creta- 
ceous and  Eocene  of  Canada. 

These  species  thus  answer  to  the  living  Sequoia  scm- 
pervirens ;  but  we  can  also  point  to  Tertiary  represen- 

*  It  is  Fareilca  Campbelli  of  Forbes. 


THE  FLORA  OF  THE  EARLY   MESOZOIC. 


185 


tativos  of  the  S.  ;'igantea.  Their  leaves  are  stiff  and 
sharp-pointed,  are  thinly  set  round  the  branches,  and  lie 
forward  in  the  same  way :  the  egg-shaped  cones  are  ia 
some  cases  similar. 

There  are,  however,  in  the  early  Tertiary  six  species, 
which  fill  up  the  gap  between  6'.  sempervirens  and  S. 
gigantea.  They  are  the  S.  Couttsim,  S.  affinis,  Lesq., 
S.  imbricata,  Hr.,  S.  sibirica,  Hr.,  8.  Heerii,  Lesq.,  and 
S.  biformis,  Lesq.  Of  these,  8.  Couttsim,  Hr.,  is  the 
most  common  and  most  important  species.  It  has  short 
leaves,  lying  olong  the  branch,  like  8.  gigantea,  and 
small,  round  cones,  like  8.  Langsdorjii  and  sempervirens. 
Bovey  Tracey  in  Devonshire  has  afforded  splendid  speci- 
mens of  cones,  seeds,  and  twigs,  which  have  been  described 
in  the  "  Philosophical  Transactions."  More  lately.  Count 
Saporta  has  described  specimens  of  cones  and  twigs  from 
Armissan.  Specimens  of  this  species  have  also  been  found 
in  the  older  Tertiary  of  Greenland,  so  that  it  must  have 
had  a  wide  range.  It  is  very  like  to  the  American  8. 
affinis,  Lesq. 

In  the  Tertiary  there  have  been  already  found  fourteen 
well-marked  species,  which  thus  include  representatives 
of  the  two  living  types,  8.  sempervirens  and  8.  gigantea. 

We  can  follow  this  genus  still  further  back.  If  we  go 
back  to  the  Cretaceous  age,  we  find  ten  species,  of  which 
five  occur  in  the  Urgon  of  the  Lower  Cretaceous,  two  in 
the  Middle,  and  three  in  the  Upper  Cretaceous.  Among 
these,  the  Lower  Cretaceous  exhibits  the  two  types  of  the 
8equoia  sempervirens  and  8.  gigantea.  To  the  former 
the  8.  8mithia?ia  answers,  and  to  the  latter,  the  Reichen- 
bacJiii,  Gein.  The  ^S'.  8mit1iiana  stands  indeed  uncom- 
monly near  the  8.  Langsdorjii,  both  in  the  appearance  of 
the  leaves  on  the  twigs  and  in  the  shape  of  the  cones. 
These  are,  however,  smaller,  and  the  leaves  do  not  become 
narrower  toward  the  base.  The  8.  pectina,  Hr.,  of  the 
Upper  Cretaceous,  has  its  leaves  arranged  in  two  rows,  and 


PI" 


186 


THE   GEOLOGICAL  HISTORY  OF  PLANTS." 


t 


!    I 


|ii'  m<  I 


» 


presents  a  similar  appearance.  The  S.  Eeichenbachii  is  a 
type  more  distinct  from  those  nc  \y  living  and  those  in 
the  Tertiary.  It  has  indeed  stiff,  pointed  leaves,  lying 
forward,  but  they  are  arcuate,  and  the  cones  are  smaller. 
Tills  tree  has  been  known  for  a  long  time,  and  it  serves 
in  the  Cretaceous  as  a  guiding  star,  which  we  can  follow 
from  the  TJrgoniaa  of  the  Lower  Cretaceous  up  to  the 
Cenomanian.  It  is  known  in  France,  Belgium,  Bohemia, 
Saxony,  Greenland,  and  Spitzbergen  (also  in  Canada  and 
the  United  States).  It  has  been  placed  in  another  genus 
— Geinitzia — but  we  can  recognise,  by  the  help  of  the 
cones,  that  it  belongs  to  Sequoia. 

Below  this,  there  is  found  in  Greenland  a  nearly  re- 
lated species,  the  S.  amhigua,  Ilr.,  of  which  the  leaves 
are  shorter  and  broader,  and  the  cones  round  and  some- 
what smaller. 

The  connecting  link  between  8.  Smitliiana  and  Reich- 
enlachii  is  formed  by  S.  suhidata,  Ilr.,  and  S.  rifjida^ 
Hr.,  and  three  species  (*S'.  gracilis,  Ilr.,  8.  fastigiata  and 
8.  Gardneriana,  Cair.),  with  leaves  lying  closely  along  the 
branch,  and  which  come  very  near  to  the  Tertiary  species 
8.  Couttsim.  We  have  therefore  in  the  Cretaceous  quite 
an  array  of  species,  which  fill  up  the  gap  between  the  8. 
sempervirens  and  gigantea,  and  show  us  that  the  genus 
Sequoia  had  already  attained  a  great  development  in  the 
Cretaceous.  This  was  still  greater  in  the  Tertiary,  in 
which  it  also  reached  its  maximum  of  geographical  dis- 
tribution. Into  the  present  world  the  two  extremes  of 
the  genus  have  alone  continued ;  the  numerous  species 
forming  its  main  body  have  fallen  out  in  the  Tertiary. 

If  we  look  still  further  back,  we  find  in  the  Jura  a 
great  number  of  conifers,  and,  among  them,  we  meet  in 
the  genus  Pinus  with  a  typo  which  is  highly  developed, 
and  which  still  survives  ;  but  for  Sequoia  we  have  till  now 
looked  in  vain,  so  that  for  the  present  we  can  not  place 
the  rise  of  the  genus  lower  than  the  Urgonian  of  the  Cre- 


THE  FLORA  OF  THE  EARLY   MESOZOIC. 


187 


1! 


taceous,  however  remarkable  we  may  think  it  that  in  that 
period  it  should  have  developed  into  so  many  species  ;  a;id 
it  is  still  more  surprising  that  two  species  already  make 
their  appearance  which  approach  so  near  to  the  living 
Sequoia  sempervirens  and  S,  gigantea. 

Altogether,  we  have  become  acquainted,  up  to  Hie 
present  time,  with  twenty-six  species  of  Sequoia.  Four- 
teen of  these  species  are  found  in  the  Arctic  zone,  and 
have  been  described  and  figured  in  the  **  Fossil  Flora 
of  the  Arctic  Eegions."  Sequoia  has  been  recognised  by 
Ettingshausen  even  in  Australia,  but  there  in  the  Eocene. 

This  is,  perhaps,  the  most  remarkub^:  record  in  the 
whole  history  of  vegetation.  The  Sequoias  are  the  giants 
of  the  conifers,  the  grandest  representatives  of  the  family, 
and  the  fact  that,  after  spreading  over  the  whole  northern 
hemisphere  "nd  attaining  to  more  than  twenty  specific 
forms,  their  decaying  remnant  should  now  be  confined  to 
one  limited  region  in  western  America  and  to  two  species 
constitutes  a  sad  memento  of  departed  greatness.*  The 
small  remnant  of  S.  gigantea  still,  however,  towers  above 
all  competitors,  as  eminently  the  "  big  trees  "  ;  but,  had 
they  and  the  allied  species  failed  to  escape  the  Tertiary 
continental  submergences  rnd  the  disasters  of  the  glacial 
period,  this  grand  genus  would  have  been  to  us  an  extinct 
type.  In  like  manner  the  survival  of  the  single  gingko 
of  eastern  Asia  alone  enables  us  to  understand  that 
great  series  of  taxine  trees  with  fern-like  leaves  of  which 
it  is  the  sole  representative. 

Besides  these  peculiar  and  now  rare  forms,  we  hu, :  in 
the  Mesozoic  many  others  related  closely  to  existing  yews, 
cypresses,  pines,  and  spruces,  so  that  the  conifers  were 
probably  in  greater  abundance  and  variety  than  they  are 
at  this  day. 

*  The  writer  has  shown  that  much  of  the  material  of  the  great  lignite 
bods  of  the  Canadian  Northwest  consists  of  wood  of  Sequoia  of  both  the 
modem  types. 


188 


THE   GEOLOGICAL   HISTORY  OF  PLANTS. 


:l-   ir 


Vi  K 


In  this  period,  also,  we  find  the  earliest  representatives 
of  the  endogenous  plants.  It  is  true  that  some  plants 
found  in  the  coal-formation  have  '^een  doubtfully  re- 
ferred to  these,  but  the  earliest  certain  ex  imples  would 
seem  to  be  some  bamboo-like  and  screw-pine-like  plants 
occurring  in  the  Jurassic  rocks.  Some  of  these  are,  it  is 
true,  doubtful  forms,  but  of  others  there  seems  to  be  no 
question.  The  modern  Pandanus  or  screw-pine  of  the 
tropical  regions,  which  is  not  a  pine,  however,  but  a 
humble  relation  of  the  palms,  is  a  stiffly  branching  tree, 
of  a  candelabra-like  form,  and  with  tufts  of  long  leaves 
on  its  branches,  and  nuts  or  great  hard  berries  for  fruit, 
borne  sometimes  in  large  masses,  and  so  protected  as  to 
admit  of  their  drifting  uninjured  on  the  sea.  The  stems 
are  supported  by  masses  of  aerial  roots  like  those  which 
strengthen  the  stems  of  tree-ferns.  These  structures  and 
habits  of  growth  fit  the  Pandanus  for  its  especial  habitat 
on  the  shores  of  tropical  islands,  to  which  its  masses  of 
nuts  are  drifted  by  tb  winds  and  currents,  and  on  whose 
shores  it  can  establish  itself  by  the  aid  of  its  aerial  roots. 

Some  plants  referred  to  the  cycads  have  proved  veri- 
table botanical  puzzles.  One  of  these,  the  Williamsonia 
gigas  of  the  English  oolite,  originally  discovered  by  my 
friend  Dr.  Williamson,  and  named  by  him  Zamia  gigas,  a 
very  tall  and  beautif  il  species,  found  in  rocks  of  this  age  in 
various  parts  of  Europe,  has  been  claimed  by  Saporta  for 
the  EnJogens,  as  a  plant  allied  to  Pandanus.  Some 
other  botanists  have  supposed  the  flowers  and  fruits  to  be 
parasites  on  other  plants,  like  the  modern  Raffiesia  of 
Sumatra,  but  it  is  possible  that  after  all  it  may  prove  to 
have  been  an  aberrant  cycad. 

The  tiee-palms  are  not  found  earlier  than  the  Middle 
Cretaceous,  where  we  shall  notice  them  in  the  next  chap- 
ter. In  like  manner,  though  a  few  Angiosperms  occur 
in  rocks  believed  to  be  Lower  or  Lower  Middle  Cretaceous 
in  Greenland  and  the  northwest  territory  of  Canada,  and 


r*'M*^»^'«v»r 


THE  FLORA  OF  THE  EARLY   MESOZOIC. 


189 


'1 


in  Virginia,  these  are  merely  precursors  of  those  of  the 
Upper  Cretaceous,  and  are  not  satHcient  to  redeem  the 
earlier  Cretaceous  from  being  a  period  of  pines  and  cycads. 

On  the  whole,  this  early  Mesozoic  flora,  so  far  as 
known  to  us,  has  a  monotonous  and  mean  appearance. 
It  no  doubt  formed  vast  forests  of  tall  pines,  perhaps  re- 
sembling the  giant  Sequoias  of  California  ;  but  they  must 
for  the  most  part  have  been  dark  and  dismal  woods, 
probably  tenanted  by  few  forms  of  life,  for  the  great  rep- 
tiles of  this  age  must  have  preferred  the  open  and  sunny 
coasts,  and  many  of  them  dwelt  in  the  waters.  Still  wo 
must  not  be  too  sure  of  this.  Tiie  berries  and  nuts  of  the 
numerous  yews  and  cycads  were  capable  of  affording 
much  food.  We  know  that  in  this  age  there  were  many 
great  herbivorous  reptiles,  like  Ifjiianodon  and  Hadrosau- 
rus,  some  of  them  fitted  by  their  structure  to  feed  upon 
the  leaves  and  fruits  of  trees.  There  were  also  several 
kinds  of  small  herbivorous  mammals,  and  much  insect 
life,  and  it  is  likely  that  few  of  the  inhabitants  of  the 
Mesozoic  woods  have  been  preserved  as  fossils.  We  may 
yet  have  much  to  learn  of  the  inhabitants  of  these  forests 
of  ferns,  cycads,  and  i)incs.  We  must  not  forget  in  this 
connection  that  in  the  present  day  there  are  large  islands, 
like  New  Zealand,  destitute  of  mammalia,  and  having  a 
flora  comparable  with  that  of  the  Mesozoic  in  the  northern 
hemisphere,  though  more  varied.  We  have  also  the  re- 
markable example  of  Australia,  with  a  much  richer  flora 
than  that  of  the  early  Mesozoic,  yet  inhabited  only  by 
non-placental  mammals,  like  those  of  the  Mesozoic. 

The  principal  legacy  that  the  Mesozoic  woods  have 
handed  down  to  our  time  is  in  some  beds  of  coal,  locally 
important,  but  of  far  less  extent  than  those  of  the  Car- 
boniferous period.  Still,  in  America,  the  Richmond  coal- 
field in  Virginia  is  of  this  age,  and  so  are  the  anthracite 
beds  of  the  Queen  Charlotte  Islands,  on  the  west  coast  of 
Canada,  and  the  coal  of  Brora  in  Sutherlandshire.  Valu- 
18 


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190 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


able  beds  of  coal,  probably  of  this  age,  also  exist  in  China, 
India,  and  South  Africa  ;  and  jet,  which  is  so  extensively 
used  for  ornament,  is  principally  derived  from  the  car- 
bonised remains  of  the  old  Mesozoic  pines. 

In  the  next  chapter  we  have  to  study  a  revolution  in 
vegetable  life  most  striking  and  unique,  in  the  advent  of 
the  forest-trees  of  strictly  modern  types.       ,       ^    ,     ;   . 


NOTE  TO  CHAPTER  V. 

I  APPEND  to  this  chapter  a  table  showing  the  plant-bearing  series 
of  the  Cretaceous  and  Laramie  of  North  America,  from  a  paper  in 
"  Trans.  R.  S.  C,"  1885,  which  see  for  further  details :  •    ;    .  ,  , 

(In  Descending  Order.) 


Period!. 

Flora*  and  tabflorag. 

Raferencni, 

Transition 

Eocene  to 

Cretaceous. 

Upper  Laramie  or  Porcu- 
pine Hill.    Fort  Union 
group,  U  S.  territory. 

Platanus  beds  of  Souris  River  and 
Calgary.    Rep<jrt  of  Geol.  Sur- 
vey of  Canada  for  1879,  and  Me- 
moir of  1885. 

Upper 
Cretaceous 

Middle  T  jvramie  or  Willow 
Creek  beds. 

Lower    Laramie    or  St. 
Mary  River. 

Fox  Hill  series 

■  Lemna  and  Plstia  beds  of  bad  lands 
of  49th  parallel,  Red  Deer  River, 
&c.,  with  lignites.    Report  49th 
I    Parallel  antlMemoir  of  1885. 
Marine. 

(Daman  and 

Fort  Pierre  series 

Marine. 

Seuonian). 

Belly  River 

j  Sequoia  and  Brasenia  beds  of  S. 
•<     Saskatchewan,  Belly  River,  &c., 

Coal  measures  of  Nanai- 
mo,  B.C.,  probably  here. 

1     with  Ugnites.    Memoir  of  1885. 
j  Memoir  of  1883.    Many  dicotyle- 
(     dons,  palms,  &c. 

Middle  Creta- 
ceous   (Tu- 
ronian  and 
Cenomani- 
an). 

Dunvegan  series  of  Peace 
River.     Dakota  group, 
U.    S.      Amboy   clays, 
U.S. 

Mill  Creek  beds  of  Rocky 
Mountains. 

Memoir  of  1883.    Many  dicotyle- 
dons, cycads,  &c. 

Dicotyledonous  leaves,  similar  to 
-      Dakota  group  of  the  U.  S.     Me- 
moir of  1885. 

Lower  Creta- 
ceous   (Ne- 
ocomian, 

&c.). 

Suskwa  River  beds  and 
Queen  Charlotte  Island 
coal  series.    Intermedi- 
ate    beds     of     Rocky 
Mountains.       Potomac 
series  of  Virginia. 

Kootanie  series  of  Rocky 
Mountains. 

Cycads,  pines,  a  few  dicotjiedons. 
Report  Geol.  Survey.     Memoir 

of  1885.                                     .        :    ,.    .V 

\  CVcads,  pines,  and  ferns.  Memoir 
>     of  1885. 

CHAPTER  VI. 

THE  REIGN  OF  ANGI3SPERMS  IN  THE  LATER  CRETACEOUS 

AND  KAINOZOIC. 

It  is  a  remarlcable  fact  in  geological  chronology  that 
the  culmination  of  the  vegetable  kingdom  antedates  that 
of  the  animal.  The  placental  mammals,  the  highest 
group  of  the  animal  kingdom,  are  not  known  till  the  be- 
ginning of  the  Eocene  Tertiary.  The  dicotyledonous 
Angiosperms,  which  correspond 
to  them  in  the  vegetable  king- 
dom, occur  far  earlier — in  the 
beginning  of  the  Upper  Cre- 
taceous or  close  of  the  Lower 
Cretaceous.  The  reign  of  cy- 
cads  and  pines  holds  through- 
out the  Lower  Cretaceous,  but 
at  the  close  of  that  age  there  is 
a  sudden  incoming  of  the  high- 
er plants,  and  a  proportionate 
decrease,  more  especially  of  the 
cycads. 

I  have  already  referred  to  the 
angiospermous   wood    supposed 
to  be  Devonian,  but  I  fear  to 
rest  any  conclusion  on  this  iso- 
lated   fact.      Beyond    this,   the  earliest    indications  of 
plants  of  this  class  have    been  found    in    the    Lower 
Cretaceous.     Many  years  ago   Heer  described  and   fig- 
ured the  leaves  of  a  poplar  {Fopulus  primceva)  from 


Fio.  68. — IbpvlusprimcEva^ 
liter.  Cretaceous,  of 
Greenland.  One  of  the 
oldest  known  Angio- 
eporuis. 


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102  THE  GEOLOGICAL  HISTORY  OF  PLANTS. 

the  supposed  Lower  Cretaceous  of  Kome,  in  Greenland 
(Fig.  G8).  Two  species,  af  Sterculia  and  a  Laurus  or 
Salix,  occur  among  fossils  described  by  me  in  the  upper 
part  of  the  Kootanie  series  of  the  llocky  Mountains,  and 
Fontaine  has  recently  found  in  the  Potomac  group  of 
Virginia — believed  to  be  of  Neoconiian  age — several  angio- 
spermous  sj)ecies  {Sassafras,  Mcnispermitesy  Sapindus, 
Aralia,  Pojmlusy  &c. )  mixed  with  a  rich  flora  of  cycads 
and  pines.  These  are  the  early  forerunners  of  the  mod- 
ern angiospermous  flora ;  but  so  far  as  known  they  do 
not  occur  below  the  Cretaceous,  and  in  its  lower  portions 
only  very  rarely.  When,  however,  we  ascend  into  the 
Upper  Cretaceous,  whether  of  Euro})e  or  America,  there 
is  a  remarkable  incoming  of  the  higher  plants,  under 
generic  forms  similar  to  those  now  existing.  This  is,  in 
truth,  the  advent  of  the  modern  flora  of  the  temperate 
regions  of  the  earth.  A  very  interesting  tabular  view  of 
its  early  distribution  is  given  by  Ward,  in  the  "American 
Journal  of  Science  "  for  1884,  of  which  the  following  is  a 
synopsis,  with  slight  emendations.  I  may  add  that  the 
new  discoveries  made  since  1884  would  probably  tend  to 
increase  the  proportionate  number  of  dicotyledons  in  the 
newer  groups. 

Dicotyledonous  Trees  in  the  Cretaceoc8. 

Upper  Senonian 179  species. 

(Fox  Hill  group  of  America.) 

Lower  Senonian 81  species. 

Upper  white  chalk  of  Europe;  Fort  Pierre 
group  of  America ;  coal-measures  of  Na- 
naimo  ? 

Turanian 20  species. 

Lower  white  chalk ;  New  Jersey  marls ; 
Belly  R.  group. 

Cenomaiiian 357  species. 

(Chalk-marl,  grcensand,  and  Gault,  Niobrara 
and   Dakota  groups   of  America) ;    Dun- 
vegan  group  of  Canada;  Amboy  clays  of 
A-       New  Jersey. 


J:!^!i 


LATER  CRETACEOUS  AND  KAINOZOIC. 


193 


Neoenmian 

(Lower  grcensand  and  Specton  clay,  Wealden 
and  Hastings  sands,  Kootanie  and  (jucca 
Charlotte  groups  of  Canada.) 


20  species; 


Thus  we  have  a  great  and  sudden  inswarming  of  the 
higher  plants  of  modern  types  at  the  close  of  the  Lower 
Cretaceous.  In  relation  to  this,  Saporta,  one  of  the  most 
enthusiastic  of  evolutionists,  is  struck  by  this  phenome- 
non of  the  sudden  appearance  of  so  many  forms,  and 
some  of  them  the  most  highly  differentiated  of  dicotyle- 
donous plants.  The  early  stages  of  their  evolution  may, 
he  thinks,  have  been  obscure  and  as  yet  unobserved,  or 
they  may  have  taken  place  in  some  separate  region,  or 
mother  country  as  yet  undiscovered,  or  they  may  have 
been  produced  by  a  rapid  and  unusual  multiplication  of 
flower-haunting  insects  !  Or  it  is  even  conceivable  that 
the  apparently  sudden  elevation  of  plants  may  have  been 
due  to  causes  still  unknown.  This  last  seems,  indeed, 
the  only  certain  inference  in  the  case,  since,  as  Saporta 
proceeds  to  say  in  conclusion  :  **  Whatever  hypothesis 
one  may  prefer,  the  fact  of  the  rapid  multiplication  of 
dicotyledons,  and  of  their  simultaneous  appearance  in 
a  great  number  of  places  in  the  northern  hemisphere  at 
the  beginning  of  the  Cenomanian  epoch,  cannot  be  dis- 
puted."! 

The  leaves  described  by  Heer,  from  the  Middle  Cre- 
taceous of  Greenland,  are  those  of  a  poplar  {P.  primcBva). 
Those  which  I  have  described  from  a  corresponding  hori- 
zon in  the  Rocky  Mountains  are  a  Sterculites  {S.  vetus- 
tula),  probably  allied  to  the  mallows,  and  an  elongated 
leaf,  Laurophyllum  (L.  crassinerve)  (Fig.  69),  which 
may,  however,  have  belonged  to  a  willow  rather  than  a 
laurel.     These  are  certainly  older  than  the  Dakota  group 


''li 


*  Including  an  estimate  of  Fontaine's  undescribed  species, 
f  "Monde  des  Plantca,"  p.  197. 


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194 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


of  tlic  United  States  and  the  corre.sponding  formations 
in  Canada.  On  the  eastern  side  of  the  American  conti- 
nent, in  Virginia,  the  Potomac  series  is  siipi)oscd  to  be 

of  Lower  Cretaceous  age, 
and  here  Fontaine,  as 
already  stated,  has  found 
an  abundant  llora  of  cy- 
cads,  conifers,  and  ferns, 
with  a  few  angiosperm- 
ous  leaves,  which  have 
not  yet  been  described. 

In  the  Canadian  Rocky 
Mountains,  ix  few  hun- 
dreds of  feet  above  the 
beds  holding  the  before- 
mentioned  species,  are  the 
shales  of  the  Mill  Creek 
scries,  rich  in  many  spe- 
cies of  dicotyledonous 
leaves,  and  corresponding  in  age  with  the  Dakota  group, 
whose  fossils  have  been  so  well  described,  first  by  Heer 
and  Capellini,  and  afterward  by  Lesquereux.  We  may 
take  this  Dakota  group  and  the  quader-sandstone  of  Ger- 
many as  types  of  the  plant-bearing  Cenomanian,  and  may 
notice  the  forms  occurring  in  them. 

In  the  first  place,  we  recognise  here  the  successors  of 
our  old  friends,  the  ferns  and  the  iiines,  the  latter  repre- 
sented by  such  genera  as  Taxites,  btquoiay  Ghjptostrobus, 
Gingko,  and  even  Pimts  itself.  We  also  have  a  few 
cycads,  but  not  so  dominant  as  in  the  previous  ages. 
The  fan-palms  are  well  represented,  both  in  America  and 
in  the  corresponding  series  in  Europe,  especially  by  the 
genus  Sabal,  which  is  the  characteristic  American  type  of 
fan-palm,  and  there  is  one  genus  which  Saporta  regards 
as  intermediate  between  the  fan-palms  and  the  pinnately 
leaved  species.     There  are  also  many  fragments  of  stems 


Fio.  69. — Rtercalia  and  L<xuroph>jllum 
or  Sdli.e,  the  oklcf*t  Aiij?iosi>ernis 
known  in  tho  Cretaceous  of  Canada. 


■^•T'^-W^r*?*!*/* 


LATER   CRETACEOUS  AND  KAINOZOIC. 


195 


ami  leaves  of  carices  and  grasses,  so  that  these  i)lants,  now 
so  importiint  to  the  nourishment  of  man  and  his  com- 
panion animals,  were  already  rei)resented. 


Fio.  70. — Vegetation  of  Later  Cretnceoua.    Exogens  and  palms.     (Atlor 

Saporta.) 

But  the  great  feature  of  the  time  was  its  dicotyle- 
donous forests,  and  I  have  only  to  enumerate  the  genera 
supposed  to  be  represented  in  order  to  show  the  richness 
of  the  time  in  plants  of  this  type.  It  may  be  necessary 
to  explain  here  that  th  generic  names  used  are  mostly 
based  on  leaves,  and  consequently  cannot  be  held  as  being 


196 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


absolutely  certain,  since  we  know  that  at  present  one 
genus  may  have  considerable  variety  in  its  leaves,  and,  on 
the  other  hand,  that  plants  of  different  genera  may  be 
very  much  alike  in  their  foliage.  There  is,  however,  un- 
doubtedly a  likeness  in  plan  or  type  of  structure  in  leaves 
of  closely  allied  plants,  and,  therefore,  if  judiciously 
studied,  they  can  be  determined  with  at  least  approxi- 
mate certainty.*  More  especially  we  can  attain  to  much 
certainty  when  the  fruits  as  well  as  the  leaves  are  found, 
and  when  we  can  obtain  specimens  of  the  wood,  showing 
its  structure.  Such  corroboration  is  not  wanting,  though 
unfortunately  the  leaves  of  trees  are  generally  found 
drifted  away  from  the  other  organs  once  connected  with 
them.  In  my  own  experience,  however,  I  have  often 
found  determinations  of  the  leaves  of  trees  confirmed  by 
the  discovery  of  their  fruit?  or  of  the  structure  of  their 
stems.  Thus,  in  the  rich  cretaceous  plant-beds  of  the 
Dunvegan  series  we  have  bt;ech-nuts  associated  in  the 
same  beds  with  loaves  referred  to  Fagus.  In  the  Laramie 
beds  I  determined  many  years  ago  nuts  of  the  Trapa 
or  water-chestnut,  and  subsequently  Lesquereux  found, 
in  beds  in  the  United  States,  leaves  which  he  referred  to 
the  same  genus.  Later,  I  found  in  collections  made  on 
the  Red  Deer  River  of  Canada  my  fruits  and  Lesquereux's 
leaves  on  the  same  slab.  The  presence  of  trees  of  the 
genera  Carya  and  Juglans  in  the  same  formation  was  in- 
ferred from  their  leaves,  and  specimens  have  since  been 
obtained  of  silicified  wood,  with  the  microscopic  structure 
of  the  modern  butternut,  ^till  we  are  willing  to  admit 
that  determinations  from  leaves  alone  are  liable  to  doubt. 
In  the  matter  of  names  of  fossil  leaves,  I  sympathise 
very  strongly  with  Dr.  Nathorst,  of  Stockholm,  in  his 

*  Great  allowance  has  to  be  made  for  the  variability  of  leaves  of  the 
same  species.  The  modern  hazel  (C.  rostrata)  is  a  case  in  point.  Its 
leaves,  from  different  parts  of  the  same  plant,  are  so  dissimilar  in  form 
and  size  that  tbey  might  readily  be  regarded  as  of  different  species. 


LATER  CRETACEOUS  AND  K  VINOZOIC. 


197 


objection  to  the  use  of  modern  generic  names  for  mere 
leaves,  and  would  be  quite  content  to  adopt  some  non- 
committal termination,  as  that  of  '^phyllum"  or  '^iies" 
suggested  by  him.  I  feel,  however,  tliat  almost  as  much 
is  taken  for  granted  if  a  plant  is  called  Corylophyllum  or 
Corylites,  as  if  called  Corylus.  In  either  case  a  judgment 
is  expressed  as  to  its  affinities,  which  if  wrong  under  the 
one  term  is  wrong  under  the  other;  and  after  so  much  haa 
been  done  by  so  many  eminent  botanists,  it  seems  inex- 
pedient to  change  the  whole  nomenclature  for  so  small 
and  questionable  an  advantage.  I  wish  it,  however,  to 
be  distinctly  understood  that  plants  catalogued  on  the 
evidence  of  leaves  alone  are  for  the  most  part  referred  to 
certain  genera  on  grounds  necessarily  imperfect,  and 
their  names  are  therefore  subject  to  correction,  as  new 
facts  may  be  obtained. 

The  more  noteworthy  modern  genera  included  in  the 
Dakota  flora,  as  catalogued  by  Lesquereux,  are  the  follow- 
ing ;  Liquidambar,  the  sweet-gum,  is  represented  both  in 
America  and  Europe,  the  leaves  resembling  those  of  the 
modern  species,  but  with  entire  edges,  which  seems  to  be 
a  common  peculiarity  of  Cretaceous  foliage.*  Populus 
(poplar),  as  already  stated,  appears  very  early  in  Green- 
land, and  continues  with  increasing  number  of  species 
throughout  the  Cretaceous  and  Tertiary.  Salix  (willow) 
appears  only  a  little  later  and  continues.  Of  the  family 
CupnUferm  we  have  Fayus  (beech),  Quercus  (oak),  and 
Castanea  (chestnut),  which  appear  together  in  the  Dakota 
group  and  its  equivalents.  Fruits  of  some  of  the  species 
are  known,  and  also  wood  showing  structure.     Bctula 


*  With  reference  to  this,  somethinf;  may  be  learned  from  the  leaves 
of  modern  trees.  In  these,  young  shoots  have  leaves  often  less  toothed 
and  serrated  than  those  of  the  adult  tree.  A  remarkable  instance  is  the 
Poj.ulns  grandidcntatnH  of  America,  the  young  shoots  of  which  have  en- 
tire leaves,  quite  unlike  except  in  venation  those  of  the  parent  tree,  aud 
having  an  aspect  very  similar  to  that  of  the  Cretaceous  poplars. 


m 


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198 


TUE  GEOLOGICAL  HISTORY   OF  PLANTS. 


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(birch)  is  representor!  by  a  few  species,  and  specimens  of 
its  peculiar  bark  are  also  common.  Alnus  (alder)  ap- 
pears in  one  species  at  least.  The  genus  Platanus  (Fig. 
71),  that  of  the  plane-trees,  represented  at  present  by  one 


Fio.  71. — Platanus  nobilis.  Newberry,  variety  baailobata.    Laramie. 

Much  reduced. 


European  and  one  American  species,  has  several  species 
in  the  Cretaceous,  though  the  plane-trees  seem  to  culmi- 
nate in  the  early  part  of  the  succeeding  Eocene,  where 
there  are  several  species  with  immense  leaves.     The  large 


'«*•-*  «r    ^  «^  'Av* I 


11 


1 


LATER  CRETACEOUS  AND   KAINOZOIC. 


199 


3f 


le 


leaves,  known  as  Credneria,  found  in  tlie  Cenomanian  of 
Europe,  and  those  called  Protophyllum  (Fig.  72)  in 
America,  appear  to  be  nearer  to  the  plane-trees  than  to 
any  others,  though  representing  an  extinct  type.  The 
laurels  are  represented  in  this  age,  and  the  American 
genus  Sassafras,  which  has  now  only  one  species,  has  not 
one  merely  but  several  species  in  the  Cretaceous.  Diofi- 
pyros,  the  persimmon-tree,  was  also  a  Cretaceous  genus. 


FiQ.  *12,— Protophyllum  boreale,  Dawson,  reduced.    Upper  Cretaceous, 

Cauada. 

The  single  species  of  the  beautiful  Liriodendron,  or  tulip- 
tree,  is  a  remnant  of  a  genus  which  had  several  Cretaceous 
species  (Figs.  74,  75).  The  magnolias,  still  well  repre- 
sented in  the  American  flora,  were  equally  plentiful  in  the 
Cretaceous  (Fig.  73).  The  walnut  family  were  well  repre- 
sented by  species  of  Juglans  (butternut)  and  Gary  a,  or 
hickory.  In  all,  no  less  than  forty-eight  genera  are  pres- 
ent belonging  to  at  least  twenty-five  '  Mes,  running 
through  the  whole  range  of  the  dicotyU  jus  exogens. 
This  is  a  remarkable  result,  indicating  a  suaden  profusion 


■iM! 

■lii.. 
;'  1 


I   \. 


Si        i: 


200 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


i'i    : 


forms  of  these  plants  of  a  very  striking  character.     It 
.s  further  to  be  observed  that  some  of  the  genera  have 

many  species  in  the  Cre- 
taceous and  dwindle  to- 
ward the  modern.  In 
others  the  reverse  is  the 
case — they  have  expand- 
ed in  modern  times.  In 
a  number  there  seems  to 
have  been  little  change. 
Dr.  Newberry  has 
given,  in  the  ''Bulletin 
of  the  Torrey  Botanical 
Club,"  an  interesting 
resume  of  the  history 
of  the  beautiful  Lirio- 
dendron,  or  tulip-tree, 
which  may  be  taken  as 
an  example  of  a  genus 
which  has  gone  down 
in  importance  in  the 
course  of  its  geological 
history. 

"The  genus  Lirio- 
dendron,  as  all  botan- 
ists know,  is  represent- 
ed in  the  present  flora 
by  a  single  species,  *  the 
tulip-tree,'  which  is  con- 
fined to  eastern  Amer- 
ica, but  grows  over  all 
the  area  lying  between 
the  Lakes  and  the  Gulf, 
the  Mississippi  and  the 
Atlantic.  It  is  a  mag- 
nificent   tree,    on    the 


r 


Fio.  73. — Maqnolia  magnifica^  Dawson, 
reduced.     iJpper  Cretaceoua,  Canada. 


r     !; 


LATER  CRETACEOUS  AND  KAINOZOIC. 


9,01 


whole,  the  finest  in  our  forests.     Its  cylindrical  trunk, 
sometimes  ten  feet  in  diameter,  carries  it  beyond  all  its 
associates  in  size,  while  the  beauty  of  its  glossy,  lyre- 
shaped  leaves  and  tulip- 
like flowers   is  only  sur- 
passed by  the  flowers  and 
foliage  of  its   first  cous- 
in, Magnolia  grandiflora. 
That  a  plant  so  splendid 


Fio.   74. — Liriodendron  Meekii^ 
Ileer.     (After  Lesqucrtux.) 


Fio.   75. — Liriodendron  primccvum^ 
Newberry.     (After  Newberry.) 


should  stand  quite  alone  in  the  vegetation  of  the  present 
day  excited  the  wonder  of  the  earlier  botanists,  but  the 
sassafras,  the  sweet-gum,  and  the  great  Sequoias  of  the  far 
West  afford  similar  examples  of  isolation,  and  the  latter 
are  still  more  striking  illustrations  of  solitary  grandeur." 
(Figs.  74  and  75.) 

**  Three  species  of  Liriodendron  are  indicated  by  leaves 
found  in  the  Amboy  clays — Middle  Cretaceous — of  New 
Jersey,  and  others  have  been  obtained  from  the  Dakota 
group  in  the  West,  and  from  the  Upper  Cretaceous  strata 
of  Greenland.  Though  differing  considerably  among 
themselves  in  size  and  fv-rm,  all  these  have  the  deep  sinus 
of  the  upper  extremity  so  characteristic  of  the  genus, 
and  the  nervation  is  also  essentially  the  same.  Hence, 
we  must  conclude  that  the  genus  Liriodendron,  now  rep- 
.19 


'.I 


!i!i 


■ 


!  ,   ' 


111*      <    1 

It 


m 


!:■ 


202 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


resented  by  a  single  species,  was  in  the  Cretaceouii  age 
much  more  largely  developed,  having  many  species,  and 
those  scattered  throughout  mary  lands.  In  the  Tertiary 
age  the  genus  continued  to  exist,  but  the  species  seem  to 
have  been  reduced  to  one,  which  is  hardly  to  be  distin- 
guished from  that  now  living.  In  many  parts  of  Europe 
leaves  of  the  tulip-tree  have  been  found,  and  it  extended 
as  far  south  as  Italy.  Its  presence  there  was  first  made 
known  by  Unger,  in  his  '  Synopsis,'  page  233,  and  in  his 
*  Genera  et  Species,'  page  443,  where  he  describes  it 
under  the  name  of  Liriodendron  procaccinii.  Tlie  genus 
has  also  been  noticed  in  Europe  by  Massalongo,  Ileer,  and 
Ettingshausen,  and  three  species  have  been  distinguished. 
All  these  are,  however,  so  much  like  the  living  species 
that  they  should  probably  be  united  with  it.  We  here 
have  a  striking  illustration  of  the  wide  distribution  of  a 
species  which  has  retained  its  characters  both  of  fruit  and 
leaf  quite  unchanged  through  long  migrations  and  an 
enormous  lapse  of  time. 

"■  In  Europe  the  tulip-tree,  like  many  of  its  American 
associates,  seems  to  have  been  destroyed  by  the  cold  of 
the  Ice  period,  the  Mediterranean  cutting  off  its  retreat, 
but  in  America  it  migrated  southward  over  the  southern 
extension  of  the  continent  and  returned  northward  again 
with  the  amelioration  of  the  climate." 

Leaves  of  Liriodendron  have  been  recognised  in  the 
Cretaceous  of  Greenland,  though  it  is  now  a  tree  of 
the  warm  temperate  region,  and  Lesquereux  describes 
several  species  from  the  Dakota  group.  But  the  genus 
has  not  yet  been  recognised  in  the  Laramie  or  in  the 
Upper  Cretaceous  of  British  Columbia.  In  the  paper 
above  quoted,  Newberry  describes  three  new  species 
from  the  Amboy  clays,  one  of  which  he  considers  iden- 
tical with  a  Greenland  form  referred  by  Heer  to  L. 
Meeki  of  the  Dakota  group.  Thus,  if  all  Lesque- 
reux's   species   are   to    be  accepted,    the  genus    begins 


LATER  CRETACEOUS  AND  KAINOZOiC. 


203 


in  the  Middle  Cretaceous  with  at  least  nine  American 
species. 

In  New  Jersey  the  Amboy  clays  are  referred  to  the 
same  age  with  the  Dakota  beds  of  the  West.  In  these 
Dr.  Newberry  has  found  a  rich  flora,  including  many 
angiosperms.  The  following  is  condensed  from  a  pre- 
liminary notice  in  the  "  Bulletin  of  the  Torrey  Botanical 
Club":* 

*'  The  flora  of  the  Amboy  clays  is  closely  related  to 
that  of  the  Dakota  group — most  of  the  genera  and  some 
of  the  species  being  identical — so  that  we  may  conclude 
they  were  nearly  contemporaneous,  though  the  absence  in 
New  Jersey  of  the  Fort  Benton  and  Niobrara  groups  of 
the  upper  Missouri  and  the  apparent  synchronism  of  the 
New  Jersey  marls  and  the  Pierre  group  indicate  that  the 
Dakota  is  a  little  the  older. 

**  At  least  one-third  of  the  species  of  the  Amboy  clays 
seem  to  be  identical  with  leaves  found  in  the  Upper  Cre- 
taceous clays  of  Greenland  and  Aachen  (Aix  la  Chapelle), 
which  not  only  indicates  a  chronological  parallelism,  but 
shows  a  remarkable  and  unexpected  similarity  in  the  vege- 
tation of  these  widely  separated  countries  in  the  middle 
and  last  half  of  the  Cretaceous  age.  The  botanical  char- 
acter of  the  flora  of  the  Amboy  clays  will  be  seen  from  the 
following  brief  synopsis  : 

"  AlgcB. — A  small  and  delicate  form,  allied  to  Chon- 
drites. 

*' Ferns. — Twelve  species,  generally  similar  and  in 
part  identical  with  those  described  by  Heer  from  the 
Cretaceous  beds  of  Greenland,  and  referred  to  the  genera 
Dicksonia,  Gleichenia,  and  Aspidium. 

"  Cycads. — Two  species,  probably  identical  with  the 
forms  from  Greenland  described  by  Ileer  under  the 
names  of  Podozamitcs  marginatus  and  P.  tenuinervis. 


*  March,  1886. 


■I 


Ml  :? 


ll 


204 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


**  Conifers. — Fourteen  species,  belonging  to  the  genera 
Moriconia,  Brachyphyllum,  Cunninghamites,  Pitius,  Se- 
quoia, and  others  referred  by  Heer  to  Juniperus,  Libo- 
cedruSy  Frenelopsis,  Thuya,  and  Dammara.  Of  these, 
the  most  abundant  and  most  interesting  are  Moriconia 
cyclotoxon — the  most  beautiful  of  conifers — and  Cunning- 
hamites elegans,  both  of  which  occur  in  the  Cretaceous 
clays  of  Aachen,  Prussia,  and  Patoot,  Greenland.  The 
Brachyphyllum  was  a  large  and  strong  species,  with  im- 
bricated cones,  eight  inches  in  length. 

"  The  angiosperms  form  about  seventy  species,  which 
include  three  of  Magnolia,  four  of  Liriodendron,  three  or 
four  of  Salix,  three  of  Celastrophyllum  (of  which  one  is 
identical  with  a  Greenland  species),  one  Celastrus  (also 
found  in  Greenland),  four  or  five  Aralias,  two  Sassafras, 
one  Cinnamomum,  one  Hedera  j  with  leaves  that  are  ap- 
parently identical  with  those  described  by  Heer  as  belong- 
ing to  Andromeda,  Cissiies,  Cornus,  Dewalquea,  Dios- 
pyros,  EucalyiAus,  Ficus,  Ilex,  Juglans,  Laurus,  Meiii- 
spermites,  Myrica,  Myrsine,  Prunus,  Rhamnus,  and 
others  not  yet  determined. 

*'  Some  of  the  Aralias  had  palmately-lobed  leaves, 
nearly  a  foot  in  diameter,  and  two  of  the  tulip-trees 
{Liriodendron)  had  leaves  quite  as  large  as  those  of  the 
living  species.  One  of  these  had  deeply  lobed  leaves,  like 
those  of  the  white  oak.  Of  the  other,  the  leaves  resem- 
bled those  of  the  recent  tulip-tree,  but  were  larger.  Both 
had  the  peculiar  emargination  and  the  nervation  of  Lirio- 
dendron. 

**  Among  the  most  interesting  plants  of  the  collection 
are  fine  species  of  Bauhinia  and  Hymenwa.  Of  these, 
the  first  is  represented  by  a  large  number  of  leaves,  some 
of  which  are  six  or  seven  inches  in  diameter.  They  are 
deeply  bilobed,  and  have  the  peculiar  and  characteristic 
form  and  nervation  of  the  leaves  of  this  genus.  Bauhi- 
nia is  a  leguminous  genus  allied  to  Cercis,  and  now  in- 


1 


LATER  CRETACEOUS  AND  KAINOZOIC. 


205 


habits  tropical  and  warm  temperate  climates  in  both 
hemispheres.  Only  one  species  occurs  in  the  United 
States,  Bauhinia  lunarioides,  Gray,  found  by  Dr.  Bige- 
low  on  the  Rio  Grande. 

'*  Ilymenma  is  anotlier  of  the  leguminosa),  and  inhab- 
its tropical  America.  A  species  of  this  genus  has  been 
found  in  the  Upper  Cretaceous  of  France,  but  quite  dif- 
ferent from  the  one  before  us,  in  which  the  leaves  are 
much  larger,  and  the  leaflets  are  united  in  a  common 
petiole,  which  is  winged  ;  this  is  a  modification  not  found 
in  the  living  species,  and  one  which  brings  it  nearer  to 
Bauhinia. 

**  But  the  most  surprising  discovery  yet  made  is  that 
of  a  number  of  quite  large  helianthoid  flowers,  which  I 
have  called  Palmanthus.  These  are  three  to  four  inches 
in  diameter,  and  exhibit  a  scaly  involucre,  enclosing  what 
much  resembles  a  fleshy  receptacle  with  achenia.  From 
the  border  of  this  radiate  a  number  of  ray  florets,  one  to 
two  inches  in  length,  which  are  persistent  and  must  have 
been  scarious,  like  those  of  Hclichrysum.  Though  these 
flowers  so  much  resemble  those  of  the  compositsB,  we  are 
not  yet  warranted  in  asserting  that  such  is  certainly  their 
character.  In  the  Jurassic  rocks  of  Europe  and  India 
some  flowers  not  very  unlike  these  have  been  found,  which 
have  been  named  WilUamsonia,  and  referred  to  cycads  by 
Carruthers.  A  similar  fossil  has  been  found  in  the  Cre- 
taceous rocks  of  Greenland,  and  named  by  Ileer  WilUam- 
sonia cretacea,  but  he  questions  the  reference  of  the  genus 
to  the  Cycadese,  and  agrees  with  Nathorst  in  considering 
all  the  species  of  WilUamsonia  as  parasitic  flowers,  allied 
to  Brugmansia  or  Rafflesia.  The  Marquis  of  Saporta 
regards  them  as  monocotyledons,  similar  to  Pandanus. 
More  specimens  of  the  flowers  now  exhibited  will  perhaps 
prove — what  we  can  now  only  regard  as  probable — that 
the  Compositae,  like  the  Leguminosm,  Magnoliacem,  Ce- 
lastracecB,  and  other  highly  organised  plants,  formed  part 


'Ml 


TT 


i 


1 


t|K 


I  1 


i     '     ! 


206 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


of  the  Cretaceous  flora.  No  composite  flowers  have  be- 
fore been  found  in  the  fossil  state,  and,  as  these  are  among 
the  most  complex  and  specialised  forms  of  florescence,  it 
has  been  supposed  that  they  belonged  only  to  the  recent 
epoch,  where  they  were  the  result  of  a  long  series  of  form- 
ative changes." 

The  above  presents  some  interesting  new  types  not 
heretofore  found  in  the  Middle  Cretaceous.  More  espe- 
cially the  occurrence  of  large  flowers  of  the  composite 
type  presents  a  startling  illustration  of  the  early  appear- 
ance of  a  very  elevated  and  complex  form.  Great  interest 
also  attaches  to  these  Amboy  beds,  as  serving,  with  those 
of  Aix  and  Greenland,  to  show  that  the  margins  of  the 
Atlantic  were  occupied  with  a  flora  similar  to  that  occur- 
ring at  the  same  time  in  the  interior  plateau  of  North 
America  and  on  the  Pacific  slope. 

The  beds  at  Aix-la-Chapelle  are,  however,  probably 
somewhat  newer  than  the  Dakota  or  Amboy  beds,  and 
correspond  more  nearly  in  age  with  those  of  the  Creta- 
ceous coal-field  of  Vancouver  Island,  where  there  is  a  very 
rich  Upper  Cretaceous  flora,  which  I  have  noticed  in  de- 
tail in  the  *'  Transactions  of  the  Royal  Society  of  Cana- 
da."* In  these  Upper  Cretaceous  beds  there  are  fan- 
palms  as  far  north  at  least  as  the  latitude  of  49°,  indicat- 
ing a  very  mild  climate  at  this  period.  This  inference  is 
corroborated  by  the  Upper  Cretaceous  flora  of  Atane  and 
Patoot  in  Greenland,  as  described  by  Heer. 

The  dicotyledonous  plants  above  referred  to  are  trees 
and  shrubs.  Of  the  herbaceous  exogens  of  the  period  we 
know  less.  Obviously  their  leaves  are  less  likely  to  find 
their  way  into  aqueous  deposits  than  the  leaves  of  trees. 
They  are,  besides,  more  perishable,  and  in  densely  wooded 
countries  there  are  comparatively  few  herbaceous  plants. 
I  have  examined  the  beds  of  mud  deposited  at  the  mouth 

♦Vol.  ii.,  1884. 


LATER  CRETACEOUS  AND   KAIXOZOIC. 


207 


of  a  woodland  streamlet,  and  have  found  them  stored  with 
the  fallen  leaves  of  trees,  but  it  was  in  vain  to  search  for 
the  leaves  of  herbaceous  plants. 

The  climate  of  North  America  and  Europe,  represented 
by  the  Cenomanian  vegetation,  is  not  tropical  but  warm 
temperate  ;  but  the  flora  was  more  uniform  than  at  pres- 
ent, indicating  a  very  equable  climate  and  the  possibility 
of  temperate  genera  existing  within  the  Arctic  circle,  and 
it  would  seem  to  have  become  warmer  toward  the  close  of 
the  period. 

The  flora  of  the  Cenomanian  is  separated  in  most 
countries  from  that  of  the  Senonian,  or  uppermost  Cre- 
taceous, by  a  marine  formation  holding  few  plants.  This 
depends  on  great  movements  of  elevation  and  depression, 
to  which  we  must  refer  in  the  sequel.  In  a  few  regions, 
however,  as  in  the  vicinity  of  the  Peace  River  in  Canada, 
there  are  plant-bearing  beds  which  serve  to  bridge  over 
the  interval  between  the 
Early  Cenomanian  and 
the  later  Cretaceous.* 

To  this  interval  also 
would  seem  to  belong 
the  Belly  River  series  of 
western  Canada,  which 
contains  important  beds 
of  coal,  but  is  closely  as- 
sociated with  the  marine 
Fort  Pierre  Mcries.  A 
very  curious  herbaceous 

plant  of  this  group,  which  I  have  named  Brasenia  an- 
tiqua,  occurs  in  the  beds  associated  with  one  of  the  coals. 
It  is  a  close  ally  of  the  modern  B.  peltata,  an  aquatic 
plant  which  occurs  in  British  Columbia  and  in  eastern 


Fio.  7*5. — Brasenia  antiqua.  Upper  Cre- 
taceous, South  Saskatchewan  River. 
Natural  size,  a,  A,  Diagrams  of  vena- 
tion, sliglitly  enlarged. 


*  See  paper  by  the  author  in  the  "  Transactions  of  the  Koyal  Society 
of  Canada,"  1882. 


208 


TUE  GEOLOGICAL  HISTORY  OF  PLANTS. 


America,  and  is  also  said  to  be  found  in  Japan,  Australia, 
and  India,  a  width  of  distribution  appropriate  to  so  old 
a  type  (Fig.  70). 

In  so  far  as  vef^etable  life  is  concerned,  the  transition 
from  the  Upper  Cretaceous  to  the  Tertiary  or  Kainozoio 
is  easy,  though  in  many  parts  of  the  world,  and  more 
especially  in  western  Europe,  there  is  a  great  gap  in  the 
deposits  between  the  upper  Chalk  and  the  lowest  Eocene. 
With  reference  to  fossil  plants,  Schimper  recognises  in 
the  Kainozoic,  beginning  with  the  oldest,  five  formations 
— Pala3ocene,  Eocene,  Oligocone,  Miocene,  and  Pliocene. 
Throughout  these  a  flora,  similar  to  that  of  the  Creta- 
ceous on  the  one  hand  and  the  modern  on  the  other, 
though  with  important  local  peculiarities,  extends.  There 
is  evidence,  however,  of  a  gradual  refrigeration,  so  that 
in  the  Pliocene  the  climates  of  the  northern  hemisphere 
were  not  markedly  different  from  their  present  character. 

In  the  first  instance  an  important  error  was  com- 
mitted by  palaeobotanists,  in  referring  to  the  Miocene 
many  deposits  really  belonging  to  the  Eocene.  This 
arose  from  the  early  study  of  the  rich  plant-bearing 
Miocene  beds  of  Switzerland,  and  from  the  similarity  of 
the  flora  all  the  way  from  the  Middle  Cretaceous  to  the 
later  Tertiary.  The  differences  are  now  being  worked 
out,  and  we  owe  to  Mr.  Starkie  Gardner  the  credit  of 
pointing  these  out  in  England,  and  to  the  Geological 
Survey  of  Canada  that  of  collecting  the  material  for 
exhibiting  them  in  the  more  northern  part  of  America. 

In  the  great  interior  plain  of  America  there  rests 
on  the  Cretaceous  a  series  of  clays  and  sandstones  with 
beds  of  lignite,  some  of  them  eighteen  feet  in  thickness. 
This  was  formerly  known  as  the  lignitic  or  lignite  Ter- 
tiary, but  more  recently  as  the  Laramie  series.  These 
beds  were  deposited  in  fresh  or  brackish  water,  in  an 
internal  sea  or  group  of  lakes  and  swamps,  when  the 
continent  was  lower  than  at  present.     They  have  been 


.^4»»i»/l  »•' 


LATER  CRETACEOUS   AND   KALVOZOIC. 


209 


studied  both  in  the  United  States  ♦  and  Canada  ;  and, 
though  tiieir  flora  was  originally  referred  by  mistake  to 
the  Miocene,  it  is  now  known  to  be  Eocene  or  Paloeocene, 
or  even  in  part  a  transition  group  between  the  latter  and 
the  Cretaceous,  'i'lie  following  remarks,  taken  chiefly 
from  recent  papers  by  the  author,  f  will  serve  to  illustrate 
this  : 

On  the  geological  map  of  Canada  the  Laramie  series, 
formerly  known  as  the  lignitic  or  lignite  Tertiary,  oc- 
curs, with  the  exception  of  a  few  outliers,  in  two  large 
areas  west  of  the  100th  meridian,  and  separated  from  each 
other  by  a  tract  of  older  Cretaceous  rocks,  over  which  the 
Laramie  beds  may  have  extended,  before  the  later  denuda- 
tion of  the  region. 

The  most  eastern  of  these  areas,  that  of  the  Souris 
River  and  Wood  Mountain,  extends  for  some  distance 
along  the  United  States  boundary,  between  the  102d  and 
109th  meridians,  and  reaches  northward  to  about  thirty 
miles  south  of  the  **  elbow"  of  the  South  Saskatchewan 
River,  which  is  on  the  parallel  of  51°  north.  In  this 
area  the  lowest  beds  of  the  Laramie  are  seen  to  rest  on 
those  of  the  Fox  Hill  group  of  the  Upper  Cretaceous, 
and  at  one  point  on  the  west  they  are  overlaid  by  beds  of 
Miocene  Tertiary  age,  observed  by  Mr.  McConnell,  of 
the  Geological  Survey,  in  the  Cypress  Hills,  and  referred 
by  Cope,  on  the  evidence  of  mammalian  remains,  to  the 
White  River  division  of  the  o'nited  States  geologists, 
which  is  regarded  by  them  as  Lower  Miocene.|  The  age 
of  the  Laramie  beds  is  thus  stratigraphically  determined 
to  be  between  the  Fox  Hill  Cretaceous  and  the  Lower 


*  See  more  especially  the  elaborate  and  valuable  reports  by  Lesque- 
reux  and  Newberry,  and  a  recent  memoir  by  Ward  on  "  Types  of  the 
Laramie  Flora,"  "  Bulletins  of  the  United  States  Geological  Survey," 
1887. 

f  "Transactions  of  the  Royal  Society  of  Canada,"  188G-'87. 

\  "  Report  of  the  Geological  Survey  of  Canada,"  1888. 


210 


TUE  GEOLOGICAL  HISTORY  OF  PLANTS. 


I  i 


Miocene.  They  are  also  undoubtedly  continuous  with 
the  Fort  Union  group  of  the  United  States  geologists  on 
the  other  side  of  the  international  boundary,  and  they 
contain  similar  fossil  plants.  They  are  divisible  into  two 
groups — a  lower,  mostly  argillaceous,  and  to  which  the 
name  of  ^'  Bad  Lands  beds "  mny  be  given,  from  the  "bad 
lands"  of  Wood  Mountain,  where  they  are  well  exposed, 
and  an  upper,  partly  arenaceous  member,  which  may  be 
named  tiie  Souris  River  or  Porcupine  Creek  division. 
In  the  lower  division  are  found  reptilian  remains  of  Upper 
Cretaceous  type,  with  some  fish  remains  more  nearly  akin 
to  those  of  the  Eocene.*  Neither  division  has  as  yet 
afforded  mammalian  remains. 

The  western  area  is  of  still  larger  dimensions,  and  ex- 
tends along  the  eastern  base  of  the  Rocky  Mountains  from 
the  United  States  boundary  to  about  the  55th  parallel  of 
latitude,  and  stretches  eastward  to  the  111th  meridian. 
In  this  area,  and  more  especially  in  its  southern  part,  the 
officers  of  the  Geological  Survey  of  Canada  have  recog- 
nised three  divisions,  as  follows  :  (1)  The  Lower  Laramie 
or  St.  Mary  River  series,  corresponding  in  its  character 
and  fossils  to  the  Lower  or  Bad  Lands  division  of  the 
other  area.  (2)  A  middle  division,  the  Willow  Creek 
beds,  consisting  of  clays,  mostly  reddish,  and  not  recog- 
nised in  the  other  area.  (3)  The  Upper  Laramie  or 
Porcupine  Hills  division,  corresponding  in  fossils,  and  to 
some  extent  in  mineral  character,  to  the  Souris  River 
beds  of  the  eastern  area. 

The  fossil  plants  collected  by  Dr.  G.  M.  Dawson  in 
the  eastern  area  were  noticed  by  the  author  in  an  appen- 
dix to  Dr.  Dawson's  report  on  the  49th  parallel,  in  1875, 
and  a  collection  subsequently  made  by  Dr.  Selwyn  was 
described  in  the  **  Report  of  the  Geological  Survey  of 
Cauada"  for  1879-80.     Those  of  the  western  area,  and 


*  Cope,  in  Dr.  G.  M.  Dawson's  "  Report  on  the  49th  Parallel." 


?i 


LATER  CRETACEOUS  AND  KAINOZOIC. 


211 


of 
id 


especially  collections  made  by  myself  near  Calgary  in 
1883,  and  by  officers  of  the  Geological  Survey  in  1884, 
have  been  described  in  the  "Transactions  of  the  Royal 
Society  of  Canada,"  vols.  iii.  and  iv. 

In  studying  these  fossil  plants,  I  have  found  that 
there  is  a  close  correspondence  between  those  of  tiie 
Lower  and  Upper  Laramie  in  the  two  areas  above  re- 
ferred to  respectively,  and  that  the  flora  of  the  Lower 
Laramie  is  somewhat  distinct  from  that  of  the  Upper, 
the  former  being  especially  rich  in  certain  aquatic  plants, 
and  the  latter  much  more  copious  on  the  whole,  and 
much  more  rich  in  remains  of  forest-trees.  This  is,  how- 
ever, possibly  an  effect  rather  of  local  conditions  than  of 
any  considerable  change  in  the  flora,  since  some  Upper 
Laramie  forms  recur  as  low  as  the  Belly  River  series  of  the 
Cretaceous,  which  is  believed  on  stratigraphical  grounds 
to  be  considerably  older  than  the  Lower  Laramie. 

With  reference  to  the  correlation  of  these  beds  with 
those  of  the  United  States,  some  difficulty  has  arisen  from 
the  tendency  of  palaeobotanists  to  refer  the  plants  of  the 
Upper  Laramie  to  the  Miocene  age,  although  in  the  re- 
ports of  Mr.  Clarence  King,  the  late  director  of  the 
United  States  Geological  Survey,  these  beds  are  classed, 
on  the  evidence  of  stratigraphy  and  animal  fossils,  as 
Upper  Cretaceous.  More  recently,  however,  and  partly 
perhaps  in  consequence  of  the  views  maintuined  by  the 
writer  since  1875,  some  change  of  opinion  has  occurred, 
and  Dr.  Newberry  and  Mr.  Lescpiereux  seem  now  in- 
clined to  admit  that  what  in  Canada  we  recognise  as 
Upper  Laramie  is  really  Eocene,  and  the  Lower  Laramie 
either  Cretaceous  or  a  transition  group  between  this  and 
the  Eocene.  In  a  recent  paper  *  Dr.  Newberry  gives  a 
comparative   table,   in   which   he  correlates   tiie   Lower 

*  Newberry,  "  Transactions  of  the  New  York  Academy,"  February, 
1886. 


212 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


I  i 


li  I 


Laramie  with  the  Upper  Cretaceous  of  Vancouver  Island 
and  the  Faxoe  and  Maestricht  beds  of  Europe,  while  he 
regards  the  Upper  Laramie  as  equivalent  to  European 
Eocene.  Excej^t  in  so  far  as  the  equivalence  of  the 
Lower  Laramie  and  Vancouver  Island  beds  is  concerned, 
this  corresponds  very  nearly  witli  the  conclusions  of  the 
writer  in  a  paper  published  last  year  * — namely,  that  we 
must  either  regard  the  Laramie  as  a  transition  Cretaceo- 
Eocene  group,  or  must  institute  our  line  of  separation  in 
the  Willow  Creek  or  Middle  Laramie  division,  which  has, 
however,  as  yet  afforded  no  fossil  plants.  I  doubt,  how- 
ever, the  equivalence  of  the  Vancouver  beds  and  the 
Lower  Laramie,  except  erhaps  in  so  far  as  the  upper 
member  of  the  former  is  concerned.  I  have  also  to  ob- 
serve that  in  the  latest  report  of  Mr.  Lesquereux  he  still 
seems  to  retain  in  the  Miocene  certain  formations  in  the 
West,  which  from  their  fossil  plants  I  should  be  inclined 
to  regard  as  Eocene,  f 

Two  ferns  occurring  in  these  beds  are  remarkable  as 
evidence  of  the  persistence  of  species,  and  of  the  pecul- 
iarities of  their  ancient  and  modern  distribution.  Onoclea 
sensibilis,  the  very  common  sensitive  fern  of  eastern 
America,  is  extremely  abundant  in  the  Laramie  beds  over 
a  great  area  in  the  West.  Mr.  Starkie  Gardner  and  Dr. 
Newberry  have  also  shown  that  it  is  identical  with  the 
Filicites  Hehridicus  of  Forbes,  from  the  early  Eocene  beds 
of  the  Island  of  Mull,  in  Scotland.  Thus  we  have  a 
species  once  common  to  Europe  and  America,  but  now 
restricted  to  the  latter,  and  which  has  continued  to  exist 
over  all  the  vast  ages  between  the  Cretaceous  and  the 
present  day.     In  the  Laramie  beds  I  have  found  asso- 


*  "  Transactions  of  the  Royal  Society  of  Canada,"  vol.  ii. 

f  While  these  sheets  were  going  through  the  press  I  receivecl  a  very 
valuable  report  of  Mr.  Lester  F.  Ward  upon  the  Laramie  of  the  United 
States.  I  have  merely  had  time  to  glance  at  this  report,  but  can  see  that 
the  views  of  the  author  agree  closely  with  those  above  expressed. 


LATER  CRETACEOUS  AND   KAINOZOIC. 


213 


ciated  with  this  species  another  and  more  delicate  fern, 
the  modern  DavalUa  {Stenloma)  tenuifoUa,  but  this,  un- 
like its  companion,  no  longer  occurs  in  America,  but  is 
found  in  the  mountains  of  Asia.  This  is  a  curious  illus- 
tration of  the  fact  that  frail  and  delicate  plants  may  be 
more  ancient  than  the  mountains  or  plains  on  which 
they  live. 

There  are  also  some  very  interesting  and  curious  facts 
in  connection  with  the  conifers  of  the  Laramie.  One  of 
the  most  common  of  these  is  a  Thuja  or  arbor  vitae  (the 
so-called  "cedar"  of  Canada).  The  Laramie  species  has 
been  named  T.  interrupta  by  Newberry,  but  it  approaches 
very  closely  in  its  foliage  to  T.  occidentalism  of  eastern 
Canada,  while  its  fruit  resembles  that  of  the  western 
species,  T.  gigantea. 

Still  more  remarkable  are  the  Sequoias  to  which  we 
have  already  referred,  but  which  in  the  Laramie  age  seem 
to  have  been  spread  over  nearly  all  North  America.  The 
fossil  species  are  of  two  types,  repreeenting  respectively 
the  modern  S.  gigantea  and  8.  sempervirens,  and  their 
wood,  as  well  as  that  of  Thuja,  is  found  in  great  abun- 
dance in  the  lignites,  and  also  in  tlie  form  of  silicified 
trunks,  and  corresponds  with  that  of  the  recent  species. 
The  Laramie  contains  also  conifers  cf  the  genera  Glypto- 
strohus,  Taxodium,  and  Taxus  ;  and  the  genus  Salishuria 
or  gingko — so  characteristic  of  the  Jurassic  and  Creta- 
ceous— is  still  represented  in  America  as  woU  as  in  Europe 
in  the  early  Eocene. 

We  have  no  palms  in  the  Canadian  or  Scottish  Paloeo- 
cene,  though  I  belicTe  they  are  found  further  south.  The 
dicotyledonous  trros  are  richly  repre'^f^nted.  Perhaps  the 
most  conspi'iious  v ere  three  spt"  les  of  Platanus,  the 
leaves  of  which  sometimes  fill  the  sandstones,  and  one  of 
which,  P.  nobilisy  dewberry,  sometimes  attains  the  gi- 
gantic size  of  a  foot  or  more  in  diameter  of  its  blade. 
The  hazels  are  represented  by  a  large-leaved  species,  C. 
20 


m 


214 


THE  GROLOGICia  HISTORY  OF  PLANTS. 


1 


;.| 


;! 


Macquarii,  and  by  leaves  ^lot  distinguishable  from  those 
of  the  modern  American  ecies,  6'.  Americana  and  C. 
rostrata.  There  are  also  chestnuts  and  oaks.  But  the 
poplars  and  willows  are  specially  abundant,  being  repre- 
sented by  no  less  than  six  species,  and  it  would  seem 
that  all  the  modern  types  of  poplar,  as  indicated  by  the 
forms  and  venation  of  the  leaves,  existed  already  in  the 
Laramie,  and  most  of  them  even  in  the  Upper  Cretaceous. 
Sassafras  is  represented  by  two  species,  and  the  beautiful 
group  of  Viburnum,  to  which  the  modern  tree-cranberry 
belongs,  has  several  fine  species,  of  some  of  which  both 
leaves  and  berries  have  been  found.  The  hickories  and 
butternuts  are  also  present,  the  horse-chestnut,  the  Ca- 
talpa  and  Sapindus,  and  some  curious  leaves  which  seem 
to  indicate  the  presence  of  the  modern  genus  Symplwro- 
carpus,  the  snow-berry  tribe. 

The  above  may  suffice  to  give  an  idea  of  the  flora  of 
the  older  Eocene  in  North  America,  and  I  may  refer  for 
details  to  the  works  of  Newberry,  Lesquereux,  and  Ward, 
already  cited.  I  must  now  add  that  the  so-called  Mio- 
cene of  Atanekerdluk,  Greenland,  is  really  of  the  same 


age,   as  also  the 


"Miocene" 


of  Mull,   in  Scotland,  of 


i  « 


Antrim,  in  Ireland,  and  of  Bovey  Tracey,  in  the  south  of 
England,  and  the  Gelinden,  or  "  Heersian  "  beds,  of  Bel- 
gium, described  by  Saporta.  In  comparing  the  American 
specimens  with  the  descriptions  given  by  Gardner  of  the 
leaf-beds  at  Ardtown,  in  Mull,  we  find,  as  already  stated, 
Onoclea  sensihilis,  common  to  both.  The  species  of 
Sequoia,  Gingico,  Taxus,  and  Glyptostrohus  are  also  iden- 
tical or  closely  allied,  and  so  are  many  of  the  dicotyledo- 
nous leaves.  For  example,  Platanoides  Hehridicus  is 
very  near  to  P.  nobilis,  and  Gorylus  Macquarrii  is  com- 
mon to  both  formations,  as  well  as  Populus  Arctica  and 
P.  Richtirdsoni.  I  may  add  that  ever  sincu  1 875-76, 
when  I  first  studied  the  Laramie  plants,  I  have  main- 
tained their  identity  with  those  of  the  Fort  Union  group 


LATER  CRETACEOUS  AND  KAINOZOIC. 


215 


of  the  United  States,  and  of  the.  so-called  Miocene  of 
McKeuzie  River  and  Greenland,  and  that  the  whole  are 
Paleocene ;  and  this  conclusion  has  now  been  confirmed 
by  the  researches  of  Gardner  in  England,  and  by  the  dis- 
covery of  true  Lower  Miocene  beds  in  the  Canadian  north- 
west, overlying  the  Laramie  or  lignite  series. 

In  a  bulletin  of  the  United  States  Geological  Sur- 
vey (1886),  Dr.  White  has  established  in  the  AVest  the 
continuous  stratigraphical  succession  of  the  Laramie  and 
the  Wahsatch  Eocene,  thus  placing  the  Laramie  con- 
formably below  the  Lower  Eocene  of  that  region.  Cope 
has  also  described  as  the  Puerta  group  a  series  of  beds 
holding  vertebrate  fossils,  and  forming  a  transition  from 
the  Laramie  to  the  "Wahsatch.  White  also  testifies  that  a 
number  of  fresh-water  mollusks  are  common  to  the  Wah- 
satch and  the  Laramie.  This  finally  settles  the  position 
of  the  Laramie  so  far  as  the  United  States  geologists  are 
concerned,  and  shows  that  the  flora  is  to  be  regarded  as 
Eocene  if  not  Upper  Cretaceous,  in  harmony  with  what 
has  been  all  along  maintained  in  Canada.  An  important 
resume  of  the  flora  has  just  been  issued  by  Ward  in  the 
bulletins  of  the  United  States  Geological  Survey  (1887). 

Before  leaving  this  part  of  the  subject,  I  would  depre- 
cate the  remark,  which  I  see  occasionally  made,  that  fossil 
plants  are  of  little  value  in  determining  geological  hori- 
zons in  the  Cretaceous  and  Tertiary.  I  admit  that  in 
these  periods  some  allowance  must  be  made  for  local 
differences  of  station,  and  also  that  there  is  a  generic 
sameness  in  the  flora  of  the  northern  hemisphere,  from 
the  Cenomanian  to  the  modern,  yet  these  local  differ- 
ences and  general  similarity  are  not  of  a  nature  to  in- 
validate inferences  as  to  age.  No  doubt,  so  long  as 
palfEobotanists  seemed  obliged,  in  deference  to  authority, 
and  to  the  results  of  investigations  limited  to  a  few  Eu- 
ropean localities,  to  group  together,  without  distinction, 
all  the  floras  of  the  later  Cretaceous  and  earlier  Tertiary, 


J 


li 


1 
f 


!. 


'  : 


3  "    " 


216 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


irrespective  of  stratigraphical  considerations,  the  subject 
lost  its  geological  importance.  But,  when  a  good  series 
has  been  obtained  in  any  one  region  of  some  extent,  the 
case  becomes  different.  Though  there  is  still  much  im- 
perfection in  our  knowledge  of  the  Cretaceous  and  Ter- 
tiary floras  of  Canada,  I  think  the  work  already  done  is 
sufficient  to  enable  any  competent  observer  to  distinguish 
by  their  fossil  plants  the  Lower,  Middle,  and  Upper  Cre- 
taceous, and  the  latter  from  the  Tertiary  ;  and,  with  the 
aid  of  the  work  already  done  by  Lesquereux  and  New- 
berry in  the  United  States,  to  refer  approximately  to  its 
true  geological  position  any  group  of  plants  from  beds  of 
unknown  age  in  the  West. 

An  important  consequence  arising  from  the  above 
statements  is  that  the  period  of  warm  climate  which 
enabled  a  temperate  flora  to  exist  in  Greenland  was  that 
of  the  later  Cretaceous  and  early  Eocene  rather  than,  as 
usually  stated,  the  Miocene.  It  is  also  a  question  admit- 
ting of  discussion  whether  the  Eocene  flora  of  latitudes 
so  different  as  those  of  Greenland,  Mackenzie  River,  north- 
west Canada,  and  the  United  States,-were  strictly  con- 
temporaneous, or  successive  within  a  long  geological 
period  in  which  climatal  changes  were  gradually  pro- 
ceeding. The  latter  statement  must  apply  at  least  to 
the  beginning  and  close  of  the  period ;  but  the  plants 
themselves  have  something  to  say  in  favour  of  contem- 
poraneity. The  flora  of  the  Laramie  is  not  a  tropical 
but  a  temperate  flora,  showing  no  doubt  that  a  much 
more  equable  climate  prevailed  in  the  more  northern 
parts  of  America  than  at  present.  But  this  equability 
of  climate  implies  the  possibility  of  a  great  geographical 
range  on  the  part  of  plants.  Thus  it  is  quite  possible 
and  indeed  highly  probable  that  in  the  Laramie  age  a 
somewhat  uniform  flora  extended  from  the  Arctic  seas 
through  the  great  central  plateau  of  America  far  to  the 
south,  and  in  like  manner  along  the  western  coast  of 


LATER  CRETACEOUS  AND   KAINOZOIC. 


217 


Euroi:>c.  It  is  also  to  be  observed  that,  as  Gardner  points 
out,  theie  are  some  differences  indicating  a  diversity  of 
climate  between  Greenland  and  England,  and  even  be- 
tween Scotland  and  Ireland  and  the  south  of  England, 
and  we  have  similar  differences,  though  not  strongly 
marked,  between  the  Laramie  of  northern  Canada  and 
that  of  the  United  States.  When  all  our  beds  of  this 
age  from  the  Arctic  sea  to  the  49th  parallel  have  been 
ransacked  for  plants,  and  when  the  palseobotanists  of  the 
United  States  shall  have  succeeded  in  unravelling  the 
confusion  which  now  exists  between  their  Laramie  and 
the  Middle  Tertiary,  the  geologist  of  the  future  will  be 
able  to  restore  with  much  certainty  the  distribution  of 
the  vast  forests  which  in  the  early  Eocene  covered  the 
now  bare  plains  of  interior  America.  Further,  since  the 
break  which  in  western  Europe  separates  the  flora  of  the 
Cretaceous  from  that  of  the  Eocene  does  not  exist  in 
America,  it  will  then  be  possible  to  trace  the  succession 
from  the  Mesozoic  flora  of  the  Trias  and  of  the  Queen 
Charlotte  Islands  and  Kootanie  series  of  the  Lower  Cre- 
taceous up  to  the  close  of  the  Eocene ;  and  to  deter- 
mine, for  America  at  least,  the  manner  and  conditions 
under  which  the  angiospermous  flora  of  the  later  Creta- 
ceous succeeded  to  the  pines  and  cycads  which  charac- 
terised the  beginning  of  the  Cretaceous  period.  In  so 
far  as  Europe  is  concerned,  this  may  be  more  difficult, 
since  the  want  of  continuity  of  land  from  ni  h  to  south 
seems  there  to  have  been  fatal  to  the  continu,  ice  of  some 
plants  during  changes  of  climate,  and  there  were  also 
apparently  in  the  Kainozoic  period  invasions  at  certain 
times  of  species  from  the  south  and  east,  which  did  not 
occur  to  the  same  extent  in  America. 

In  recent  reports  on  the  Tertiary  floras  of  Australia 
and  New  Zealand,*  Ettingshausen  holds  that  the  flora  of 


ll'i 


«  (i 


Geological  Magazine,"  August,  1887. 


w 


M 


11 


'  • 


11 


f  f   1 


i 


I       I 


21P 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


t^  tiary,  as  a  whole,  was  of  a  generalised  character ; 

i  now  confined  to  the  southern  and  northern  hemi- 

xcres  respectively  being  then  common  to  both.  It 
would  thus  seem  that  the  present  geographical  diversities 
must  have  largely  arisen  from  the  great  changes  in  cli- 
mate and  distribution  of  land  and  water  in  the  later 
Tertiary. 

The  length  of  our  discussion  of  the  early  angiosperm- 
ous  flora  does  not  permit  us  to  trace  it  in  detail  through 
the  Miocene  and  Pliocene,  but  we  may  notice  the  con- 
nection through  these  in  the  next  chapter,  and  may  refer 
to  the  magnificent  publications  of  Heer  and  Lesquereux 
on  the  Tertiary  floras  of  Europe  and  America  respect- 
ively. 


CHAPTER  VII. 

PLANTS    FROM    THE   TERTIARY  TO  THE    MODERN   PERIOD. 

It  may  be  well  to  begin  this  chapter  with  a  sketch  of 
the  general  physical  and  geological  conditions  of  the  pe- 
riod which  was  characterised  by  the  advent  and  culmina- 
tion of  the  dicotyledonous  trees. 

In  the  Jurassic  and  earliest  Cretaceous  periods  the 
prevalence,  over  the  whole  of  the  northern  hemisphere 
and  for  a  long  time,  of  a  monotonous  assemblage  of  gym- 
nospermous  and  acrogenous  plants,  implies  a  uniform 
and  mild  climate,  and  facility  for  intercommunication  in 
the  north.  Toward  the  end  of  the  Jurassic  and  beginning 
of  the  Cretaceous,  the  land  of  the  northern  hemisphere  was 
assuming  greater  dimensions,  and  the  climate  probably 
becoming  a  little  less  uniform.  Before  the  close  of  the 
Lower  Cretaceous  period  the  dicotyledonous  flora  seems 
to  have  been  introduced,  under  geographical  conditions 
which  permitted  a  warm  temperate  climate  to  extend  as 
far  north  as  Greenland. 

In  the  Cenomanian  or  Middle  Cretaceous  age  we  find 
the  northern  hemisphere  tenanted  with  dicotyledonous 
trees  closely  allied  to  those  of  modern  times,  though  still 
indicating  a  climate  much  warmer  than  that  which  at 
present  prevails.  In  this  age,  extensive  but  gradual  sub- 
mergence of  land  is  indicated  by  the  prevalence  of  chalk 
and  marine  limestones  over  the  surface  of  both  conti- 
nents; but  a  circumpolar  belt  seems  to  have  been  main- 
tained, protecting  the  Atlantic  and  Pacific  basins  from 


■\1 


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I' 

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m- 


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220 


THE  GEOLOGICAL  F^STORY  OP  PLANTS. 


floating  ico,  and  permitting  a  temperate  flora  of  great 
richness  to  prevail  far  to  the  north,  and  especially  along 
the  southern  margins  and  extensions  of  the  circumpolar 
land.  These  seem  to  have  been  the  physical  conditions 
which  terminated  the  existence  of  the  old  Mesozoic  flora 
and  introduced  that  of  the  Middle  Cretaceous. 

As  time  advanced  the  quantity  of  land  gradually  in- 
creased, and  the  extension  of  new  plains  along  the  older 
ridges  of  land  was  coincident  with  the  deposition  of  the 
great  Laramie  series,  and  with  the  origination  of  its  pe- 
culiar flora,  which  indicates  a  mild  climate  and  consider- 
able variety  of  station  in  mountain,  plain,  and  swamp, 
as  well  as  in  great  sheets  of  shallow  and  weedy  fresh 
water. 

In  the  Eocene  and  Miocene  periods,  the  continents 
gradually  assumed  their  present  form,  and  the  vegetation 
became  still  more  modern  in  aspect.  In  that  period  of 
the  Eocene,  however,  in  which  the  great  nummulitic 
limestones  were  deposited,  a  submergence  of  land  occurred 
on  the  eastern  continent  which  must  have  assimilated  its 
physical  conditions  to  those  of  the  Middle  Cretaceous. 
This  great  change,  affecting  materially  the  flora  of  Eu- 
rope, was  not  equally  great  in  America,  which  also  by  the 
north  and  south  extension  of  its  mountain-chains  per- 
mitted movements  of  migration  not  possible  in  the  Old 
World.  From  the  Eocene  downward,  the  remains  of 
land-animals  and  plants  are  found  chiefly  in  lake-basins 
occupying  the  existing  depressions  of  the  land,  though 
more  extensive  than  those  now  remaining.  It  must  also 
be  borne  in  mind  that  the  great  foldings  and  fractures  of 
the  crust  of  the  earth  which  occurred  at  the  close  of  the 
Eocene,  and  to  which  the  final  elevation  of  such  ranges 
as  the  Alps  and  the  Rocky  Mountains  belongs,  perma- 
nently modified  and  moulded  the  forms  of  the  continents. 

These  statements  raise,  however,  questions  as  to  the 
precise  equivalence  in  time  of  similar  floras  found  in  dif- 


THE  TKRTIARY  TO  THE  MODERN  PERIOD. 


221 


ferent  lutitudes.  However  equable  the  climate,  there 
must  have  been  some  appreciable  difference  in  proceed- 
ing from  north  to  south.  If,  therefore,  as  seems  in 
every  way  probable,  the  new  species  of  plants  origi- 
nated on  the  Arctic  land  and  spread  themselves  south- 
ward, this  latter  process  would  occur  most  naturally  in 
times  of  gradual  refrigeration  or  of  the  access  of  a 
more  extreme  climate — that  is,  in  times  of  the  elevation 
of  land  in  the  temperate  latitudes,  or,  conversely,  of 
local  depression  of  land  in  the  Arctic,  leading  to  invasions 
of  northern  ice.  Hence,  the  times  of  the  prevalence  of 
particular  types  of  plants  in  the  far  north  would  precede 
those  of  their  extension  to  the  south,  and  a  flora  found 
fossil  in  Greenland  might  be  supposed  to  be  somewhat 
older  than  a  similar  flora  when  found  farther  south.  It 
would  seem,  however,  that  the  time  required  for  the  ex- 
tension of  a  new  flora  to  its  extreme  geographical  limit  is 
so  small,  in  comparison  with  the  duration  of  an  entire 
geological  period,  that,  practically,  this  difference  is  of 
little  moment,  or  at  least  does  not  amount  to  antedating 
the  Arctic  flora  of  a  particular  type  by  a  whole  period, 
but  only  by  a  fraction  of  such  period. 

It  does  not  appear  that,  during  the  whole  of  the  Cre- 
taceous and  Eocene  periods,  there  is  any  evidence  of  such 
refrigeration  as  seriously  to  interfere  with  the  flora,  but 
perhaps  the  times  of  most  considerable  warmth  are  those 
of  the  Dunvrgan  group  in  the  Middle  Cretaceous,  and 
those  of  the  later  Laramie  and  oldest  Eocene. 

It  would  appear  that  no  cause  for  the  mild  tempera- 
ture of  the  Cretaceous  needs  to  be  invoked,  other  than 
those  mutations  of  land  and  water  which  the  geological 
deposits  themselves  indicate.  A  condition,  for  example, 
of  the  Atlantic  basin  in  which  the  high  land  of  Greenland 
should  be  reduced  in  elevation,  and  at  the  same  time  the 
northern  inlets  of  the  Atlantic  closed  against  the  invasion 
of  Arctic  ice,  would  at  once  restore  climatic  conditions 


II 


II 


m 


222 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


allowing  of  the  growth  of  a  temperate  flora  in  Greenland. 
As  Dr.  Brown  has  shown,*  and  as  I  have  elsewhere 
argued,  the  absence  of  light  in  the  Arctic  winter  is  no 
disadvantage,  since,  during  the  winter,  the  growth  of 
deciduous  trees  is  in  any  case  suspended  ;  while  the  con- 
stant continuance  of  light  in  the  summer  is,  on  the  con- 
trary, a  very  great  stimulus  and  advantage. 

It  is  a  remarkable  phenomenon  in  the  history  of  gen- 
era of  plants  in  the  later  Mesozoic  and  Tertiary,  that  the 
older  genera  appear  at  once  in  a  great  number  of  specific 
types,  which  become  reduced  as  well  as  limited  in  range 
down  to  the  modern.  This  is,  no  doubt,  connected  with 
the  greater  differentiation  of  local  conditions  in  the  mod- 
ern ;  but  it  indicates  also  a  law  of  rapid  multiplication  of 
species  in  the  early  life  of  genera.  The  distribution  of  the 
species  of  Salisburittj  Sequoia,  Platanus,  Sassafras,  Lirio- 
dendron,  Magnolia,  and  many  other  genera,  affords  re- 
markable proofs  of  this. 

Gray,  Saporta,  Ileer,  Newberry,  Lesqncreux,  and 
Starkie  Gardner  have  all  ably  discussed  these  points  ;  but 
the  continual  increase  of  our  knowledge  of  the  several 
floras,  and  the  removal  of  error  as  to  the  dates  of  their 
appearance,  must  greatly  conduce  to  clearer  and  more 
definite  ideas.  In  particular,  the  prevailing  opinion  that 
the  Miocene  was  the  period  of  the  greatest  extension  of 
warmth  and  of  a  temperate  flora  into  the  Arctic,  must 
be  abandoned  in  favour  of  the  later  Cretaceous  and 
Eocene  ;  and,  if  I  mistake  not,  this  will  be  found  to  ac- 
cord better  with  the  evidence  of  general  geology  and  of 
animal  fossils. 

In  these  various  revolutions  of  the  later  Cretaceous 
and  Kainozoic  periods,  America,  as  Dr.  Gray  has  well 
pointed  out,  has  had  the  advantage  of  a  continuous  stretch 
of  high  land  from  north  to  south,  affording  a  more  sure 


*  t( 


Florula  Discoana." 


TUE  TERTIARY  TO  THE  MODERN  PERIOD. 


223 


refuge  to  plants  in  times  of  submergence,  and  means  of 
escape  to  the  south  in  times  of  refrigeration.  Hence, 
the  greater  continuity  of  American  vegetation  and  tlie 
survival  of  genera  like  Sequoia  and  Liriodendron,  which 
have  perished  in  the  Old  World.  Still,  there  are  some  ex- 
ceptions to  this,  for  the  gingko-tree  is  a  case  of  survival  in 
Asia  of  a  type  once  plentiful  in  America,  but  now  extinct 
there.  Eastern  Asia  has  had,  however,  some  considerable 
share  of  the  same  advantage  possessed  by  America,  with 
the  addition,  referred  to  by  Gray,  of  a  better  and  more 
insular  climate. 

But  our  survey  of  these  physical  conditions  can  not  be 
considered  complete  till  we  shall  have  considered  the 
great  Glacial  age  of  the  Pleistocene.  It  is  certain  that 
throughout  the  later  Miocene  and  Pliocene  the  area  of  land 
in  the  northern  hemisphere  was  increasing,  and  the  largo 
and  varied  continents  were  tenanted  by  the  noblest  vege- 
tation and  the  grandest  forms  of  mammalian  life  that  the 
earth  has  ever  witnessed.  As  the  Pliocene  drew  to  a 
close,  a  gradual  diminution  of  warmth  came  on,  and 
more  especially  a  less  equable  climate,  and  this  was  ac- 
companied with  a  subsidence  of  the  land  in  the  temperate 
regions  and  with  changes  of  the  warm  ocean-currents. 
Thus  gradually  the  summers  became  cooler  and  the 
winters  longer  and  more  severe,  the  hill-tops  became 
covered  with  permanent  snows,  glaciers  ploughed  their 
way  downward  into  the  plains,  and  masses  and  fields  of 
floating  ice  cooled  the  seas.  In  these  circumstances  the 
richer  and  more  delicate  forms  of  vegetation  must  have 
been  chilled  to  death  or  obliged  to  remove  farther  south, 
and  in  many  extensive  regions,  hemmed  in  by  the  advance 
of  the  sea  on  the  one  hand  and  land-ice  on  the  other,  they 
must  have  altogether  perished. 

Yet  even  in  this  time  vegetation  was  not  altogether 
extinct.  Along- the  Gulf  of  Mexico  in  America,  and  in 
the  Mediterranean  basin  in  Europe,  there  were  still  some 


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224 


THE   GEOLOGICAL   HISTORY  OF  PLANTS. 


remains  of  a  moderate  climate  and  certain  boreal  and 
arctic  forms  moving  southward  continued  to  exist  here 
and  there  in  somewhat  high  latitudes,  just  as  similar 
plants  now  thrive  in  Grinnell  Land  within  sight  of  the 
snows  of  the  Greenland  mountains.  A  remarkable  sum- 
mary of  some  of  these  facts  as  they  relate  to  England  was 
given  by  an  eminent  English  botanist,  Mr.  Carruthers,  in 
his  address  as  President  of  the  Biological  Section  of  the 
British  Association  at  Birmingham  in  1886.  At  Cromer, 
on  the  coast  of  Norfolk,  the  celebrated  forest-bed  of  new- 
er Pliocene  age,  and  containing  the  remains  of  a  copious 
mammalian  fauna,  holds  also  remains  of  plants  in  a  state 
admitting  of  determination.  These  have  been  collected 
by  Mr.  Reid,  of  the  Geological  Survey,  and  were  reported 
on  by  Carruthers,  who  states  that  they  represent  a  some- 
what colder  temperature  than  that  of  the  present  day.  I 
quote  the  following  details  from  the  address. 

With  reference  to  the  plants  of  the  forest-bed  or 
newer  Pliocene  he  remarks  as  follows  : 

*'  Only  one  species  (Trapa  nafans,  Willd.)  has  disap- 
peared from  our  islands.  Its  fruits,  which  Mr.  llcid 
found  abundantly  in  one  locality,  agree  with  those  of  the 
plants  found  until  recently  in  the  lakes  of  Sweden.  Four 
species  (Prunus  speciosa,  L.,  Q^nanthe  Tichenalii,  Sm., 
Potamogeton  pterophylhis,  Sch.,  and  Pinus  abies,  L.) 
are  found  at  present  only  in  Europe,  and  a  fifth  {Pota- 
mogeton triclioides,  Cham.)  extends  also  to  North  Ameri- 
ca ;  two  species  (Peucedanum  palustre,  Moench,  and 
Pinus  sylvestris,  L.)  are  found  also  in  Siberia,  while  six 
more  {Sanguisorha  officinalis,  L.,  Rubies  fruticosus,  L., 
Cornus  sanguinm,  L.,  Euphorbia  amygdaloidcs,  L., 
Quercus  robur,  L.,  and  Potamogeton  crispus,  L.)  extend 
into  western  Asia,  and  two  {Fag us  sylvatica,  L.,  and 
Alnus  glutinosa,  L.)  are  included  in  the  Japanese  flora. 
Seven  species,  while  found  with  the  others,  enter  also  into 
the  Mediterranean  flora,  extending  to  North  Africa  :  these 


THE  TERTIARY  TO  THE  MODERN  PERIOD. 


225 


are  Tlmlidrum  minus,  L.,  Tlialictrum  jlavum,  L.,  Ra- 
nunculus repots,  L.,  iStellaria  aquaiica,  Scop.,  Corylus 
aveUana,  L.,  Yajinichellia  palustris,  L.,  and  Cladium 
mariscus,  Br.  With  a  similar  distribution  in  the  Old 
World,  eight  species  {Bidens  tripartita,  L.,  Mijosotis 
ccBspitosa,  Schultz,  Suceda  maritima,  Dum.,  CWatophyl- 
lum  demersu?n,  L.,  Sparganium  ramosum,  Iluds.,  Pota- 
moyeton  pectinatus,  L.,  Carex  paliidosa,  Good.,  and  Os- 
munda  "^egalis,  L.)  are  found  also  in  North  America.  Of 
the  remainder,  ten  species  {Nuphar  lutenm,  Sm.,  Meny- 
anihes  trifoliata,  L.,  Stachys palustris,  L.,  Rumex  mari- 
timus,  L.,  Rumex  acetosella,  L.,  Betula  alba,  L.,  Scirpus 
paucifiomis,  Liglitf.,  Taxus  baccata,  L.,  and  Isoetes  la- 
custris,  L. )  extend  round  the  north  temperate  zone,  while 
three  {Lycopus  europmus,  L.,  Alisma  plantago,  L.,  and 
Phragmites  communis,  Trin.),  having  the  same  distribu- 
tion in  the  north,  are  found  also  in  Australia,  and  one 
{Hippuris  vulgaris,  L.)  in  the  south  of  South  America. 
The  list  is  completed  by  Ranunculus  aquatilis,  L.,  dis- 
tributed over  all  the  temperate  regions  of  the  globe,  and 
Scirpus  lacustris,  L.,  which  is  found  in  many  tropical 
regions  as  well." 

•  He  remarks  that  these  plants,  while  including  species 
now  very  widely  scattered,  present  no  appreciable  change 
of  characters. 

Above  this  bed  are  glacial  clays,  which  hold  other 
species  indicating  an  extremely  cold  climate.  They  are 
few  in  number,  only  Salix  polaris,  a  thoroughly  arctic 
species,  and  its  ally,  S.  cinerea,  L.,  and  a  moss,  Hypiinm 
turgescens,  Schimp.,  no  longer  found  in  Britain,  but  an 
Alpine  and  arctic  species.  This  bed  belongs  to  the  begin- 
ning of  the  Glacial  period,  the  deposits  of  which  have  as 
yet  afforded  no  plants  in  England.  But  4)lants  occur  in 
post-glacial  and  upper-glacial  beds  in  different  parts  of 
T^<ngland,  to  which  Carruthers  thus  refers  : 

*The  period  of  great  cold,  during  which  arctic  ice 
81 


226 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


extended  far  into  temperate  regions,  was  not  favorable  to 
vegetable  life.  But  in  some  localities  we  have  stratified 
clays  with  plant-remains  later  than  the  Glacial  epoch, 
yet  indicating  that  the  great  cold  had  not  then  entirely 
disappeared.  In  the  lacustrine  beds  at  Holderness  is 
found  a  small  birch  {Betula  nana,  L.),  now  limited  in 
Great  Britain  to  some  of  the  mountains  of  Scotland,  but 
found  in  the  arctic  regions  of  the  Old  and  New  World 
and  on  Alpine  districts  in  L  ipe,  and  with  it  Prunus 
padus,  L.,  Quercus  rohur,  L.,  Corylus  avellana,  L., 
Alnus  glutinosa,  L.,  and  Pinus  sylvcstris,  L.  In  the 
white  clay-beds  at  Bovey  Tracey  of  the  same  age  there 
occur  the  leaves  of  Arctostaphylos  uva-ursi,  L.,  three 
species  of  willow,  viz.,  Salix  cinerea,  L.,  S.  myrtilloides, 
L.,  and  S.  polaris,  Wahl.,  and  in  addition  to  our  Alpine 
Betula  nana,  L.,  the  more  familiar  B.  alba,  L.  Two  of 
these  plants  have  been  lost  to  our  flora  from  the  change 
of  climate  that  has  taken  place,  viz.,  Salix  myrtilloides, 
L.,  and  8.  polaris,  Wahl.;  and  Betula  nana,  L.,  has  re- 
treated to  the  mountains  of  Scotland.  Three  others 
{Dryas  octopetala,  L.,  ArctostapJiylos  uva-tirsi,  L.,  and 
Salix  herhacea,  L.)  have  withdrawn  to  the  mountains  of 
northern  England,  Wales,  and  Scotland,  while  the  re- 
mainder are  still  found  scattered  over  the  country.  Not- 
withstanding the  diverse  physical  conditions  to  which 
these  plants  have  been  subjected,  the  remains  preserved 
in  these  beds  present  no  characters  by  which  tliey  can 
be  distinguished  from  the  living  representatives  of  the 
species." 

One  of  the  instances  referred  to  is  very  striking.  At 
Bovey  Tracey  the  arctic  beds  rest  directly  on  those  hold- 
ing the  rich,  warm  temj>erate  flora  of  the  Eocene  ;  so 
that  here  we  have  the  evidence  of  fossil  plants  to  show  the 
change  from  the  climate  of  the  Eocene  to  that  of  arctic 
lands,  and  the  modern  vegetation  to  indicate  the  return 
of  a  warm  temperature. 


THE   TERTIARY  TO  THE  MODERN   PERIOD. 


227 


In  Canada,  in  the  Pleistocene  beds  known  as  the  Leda 
clays,  intervening  between  the  lower  boulder  clay  and 
the  Saxicava  sand,  which  also  holds  boulders,  there  are 
beds  holding  fossil  plants,  in  some  places  intermixed  with 
sea-shells  and  bones  of  marine  fishes,  showing  that  they 
were  drifted  into  the  sea  at  a  time  of  submergence. 
These  remains  are  boreal  rather  than  arctic  in  character, 
and  with  the  remains  of  drift-wood  often  found  in  the 
boulder  deposits  serve  to  indicate  that  there  were  at  all 
times  oases  of  hardy  life  in  the  glacial  deserts,  just  as  we 
find  these  in  polar  lands  at  the  present  day.  I  condense 
from  a  paper  on  these  plants*  the  following  facts,  with  a 
few  additional  notes  : 

The  importance  of  all  information  bearing  on  the 
temperature  of  the  Post  -  pliocene  period  invests  with 
much  interest  the  study  of  the  land-plants  preserved  in 
deposits  of  this  age.  Unfortunately,  these  are  few  in  num- 
ber, and  often  not  well  preserved.  In  Canada,  though 
fragments  of  the  woody  parts  of  plants  occasionally  occur 
in  the  marine  clays  and  sands,  there  is  only  one  locality 
which  has  afforded  any  considerable  quantity  of  remains 
of  their  more  perishable  parts.  This  is  the  well-known 
deposit  of  Leda  clay  at  Green's  Creek,  on  the  Ottawa, 
celebrated  for  the  perfection  in  which  the  skeletons  of 
the  capelin  and  other  fishes  are  preserved  in  the  calcareous 
nodules  imbedded  in  the  clay.  In  similar  nodnles,  con- 
tained apparently  in  a  layer  somewhat  lower  than  that 
holding  the  ichthyolites,  remains  of  land-plants  are  some- 
what abundant,  and,  from  their  association  with  shells  of 
Leda  (jlacialis,  seem  to  have  been  washed  u^wn  from  the 
land  into  deep  water.  The  circumstances  would  seem  to 
have  been  not  dissimilar  from  those  at  present  existing 
in  the  northeast  arm  of  Gaspe  Basin,  where  I  have  dredged 
from  mud  now  being  deposited  in  deep  water,  living 

*  "Canadian  Naturalist,"  1866. 


m 


228 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


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ir' 


I    : 


specimens  of  Leda  limatula,  mixed  with  remains  of  land- 
plants. 

The  following  are  the  species  of  plants  recognised  in 
these  nodules  : 

1.  Drosera  roHindifolia,  Linn.  In  a  calcareous  nodule 
from  Green's  Creek,  the  leaf  only  preserved.  This  plant 
is  common  in  bogs  in  Canada,  Nova  Scotia,  and  New- 
foundland, and  thence,  according  to  Hooker,  to  the  Arctic 
circle.     It  is  also  European. 

3.  Acer  spicatum,  Lamx.  {Acer  montanum,  Alton.) 
Leaf  in  a  nodule  from  Green's  Creek.  Found  in  Nova 
Scotia  and  Canada,  also  at  Lake  Winnipeg,  according  to 
Richardson. 

3.  Potcntilla  Ca?iadensif,  Linn.  In  nodules  from 
Green's  Creek  ;  leaves  only  preserved.     I  have  had  some 

difficulty  in  determining  these, 
but  believe  they  must  be  referred 
to  the  species  above  named,  or 
to  P.  simplex,  Michx.,  supposed 
by  Hooker  and  Gray  to  be  a  va- 
riety. It  occurs  in  Canada  and 
New  England,  but  I  have  no  in- 
formation as  to  its  range  north- 
ward. 

4.  Gaylussaccia  resinosa,  Tor- 
rey  and  Gray.  Leaf  in  nodule 
at  Green's  Creek.  Abundant  in 
New  England  and  in  Canada, 
also  on  Lake  Huron  and  the  Saskatchewan,  according  to 
Richardson  (Fig.  77). 

5.  Popiilus  halsamifcra,  Linn.  Leaves  and  branches 
in  nodules  at  Green's  Creek.  This  is  by  much  the  most 
common  species,  and  its  leaves  are  of  small  size,  as  if  from 
trees  growing  in  cold  and  exposed  situations.  The  species 
is  North  American  and  Asiatic,  and  abounds  in  New  Eng- 
land and  Canada.     It  extends  to  the  Arctic  circle,  and  is 


Fia.  77. — Oajilufisaccia  resi- 
nosa. Pleistocene,  Can- 
ada. 


THE  TERTIARY   TO   THE   MODERN  PERIOD. 


229 


abundant  on  the  shores  of  the  Great  Slave  Lake  and  on 
tlie  McKenzie  River,  and  according  to  Richardson  con- 
stitutes much  of  the  drift  timber  of  the  Arctic  coast 
(Fig.  78). 

6.  Thuja  occidentalis,  Linn.  Trunks  and  branches 
in  the  Leda  clay  at  Montreal.  This  tree  occurs  in  New 
England  and  Canada,  and  extends  northward  into  the 


Fig.  78. — Populus  balsam i/era.    Pleistocene,  Canada. 

Hudson  Bay  territories.  It  is  a  northern  though  not 
arctic  species  in  its  geogra})hical  range.  According  to 
Lyell  it  occurs  associated  with  the  bones  of  Mastodon  in 
New  Jersey.  From  the  great  durability  of  its  wood,  it  is 
one  of  the  trees  most  likely  to  be  preserved  in  aqueous 
deposits. 

7.  Potamofjcton  perfoliatus,  Linn.  Leaves  and  seeds 
in  nodules  at  Green's  Creek.  Inhabits  streams  of  the 
Northern  States  and  Canada,  and  according  to  Richard- 
son extends  to  Great  Slave  Lake. 

8.  Potamogeton  jmsUlus.  Quantities  of  fragments 
which  I  refer  to  this  species  occur  in  nodules  at  Green's 
Creek.  They  may  possibly  belong  to  a  variety  of  P. 
hybridus  which,  together  with  P.  natans,  now  grows  in 


1 

j: 

1 

\<: 

i  ;  ■ 

it 

230 


THE   GEOLOGICAL   HISTORY   OF  PLANTS. 


the  river  Ottawa,  where  it  flows  over  the  beds  containing 
these  fossils. 

9.  CaricecD  and  Graminem.  Fragments  in  nodules 
from  Green's  Creek  appear  to  belong  to  plants  of  these 
groups,  but  I  cannot  venture  to  determine  their  species. 

10.  Equisetum  scirpoides,  Michx.  Fragments  in  nod- 
ules, Green's  Creek.  This  is  a  widely  distributed  spe- 
cies, occurring  in  the  Northern  States  and  Canada. 

11.  Fontmalis.      In  nodules  at  Green's  Creek  there 
occur,  somewhat  plentifully,  branches  of  a  moss  appar- 
ently of  the  genus  Fon- 
tinalis. 

12.  AlgcB.  With  the 
plants  above  mentioned, 
both  at  Green's  Creek 
and  at  Montreal,  there 
occur  remains  of  sea- 
weeds (Fig.  79).  They 
seem  to  belong  to  the 
genera  Fucus  and  Ulva^ 
but  I  cannot  determine 
the  species.  A  thick 
stem  in  one  of  the  nod- 
ules would  seem  to  indi- 
cate a  large  Laminaria. 


Fio.  79. — Frond  of  Fucus.    Pleisto- 
cene, Cuniida. 


With  the  above  there  are 
found  at  Green's  Creek  a 
number  of  fragments  of  leaves,  stems,  and  fruits,  which 
I  have  not  been  able  to  refer  to  their  species,  principally 
on  account  of  their  defective  state  of  preservation. 

None  of  the  plants  above  mentioned  is  properly  arctic 
in  its  distribution,  and  the  assemblage  may  be  character- 
ised as  a  selection  from  the  present  Canadian  flora  of  some 
of  the  more  hardy  species  having  the  most  northern 
range.  Green's  Creek  is  in  the  central  part  of  Canada, 
near  to  the  parallel  of  46°,  and  an  accidental  selection 


'W 


THE  TERTIARY  TO  TUE  MODERN  PERIOD. 


231 


from  its  present  flora,  though  it  might  contain  the  same 
species  found  in  the  nodules,  would  certainly  include  with 
these,  or  instead  of  some  of  them,  more  southern  forms. 
More  especially  the  balsam  poplar,  though  that  tree  oc- 
curs plentifully  on  the  Ottawa,  would  not  be  so  pre- 
dominant. But  such  an  assemblage  of  drift-plants  might 
be  furnished  by  any  American  stream  flowing  in  the  lati- 
tude of  50°  to  55°  north.  If  a  stream  flowing  to  the 
north,  it  might  deposit  these  plants  in  still  more  northern 
latitudes,  as  the  McKenzie  River  does  now.  If  flowing 
to  the  south,  it  might  deposit  them  to  the  south  of  50°. 
In  the  case  of  the  Ottawa,  the  plants  could  not  have  been 
derived  from  a  more  southern  locality,  nor  probably  from 
one  very  far  to  the  north.  We  may  therefore  safely  as- 
sume that  the  refrigeration  indicated  by  these  plants 
would  place  the  region  bordering  the  Ottawa  in  nearly  the 
same  position  with  that  of  the  south  coast  of  Labrador 
fronting  on  the  Gulf  of  St.  Lawrence  at  present.  The 
absence  of  all  the  more  arctic  species  occurring  in  Lab- 
rador should  perhaps  induce  us  to  infer  a  somewhat 
milder  climate  than  this. 

The  moderate  amount  of  refrigeration  thus  required 
would  in  my  opinion  accord  very  well  with  the  probable 
conditions  of  climate  deducible  from  the  circumstances  in 
which  the  fossil  plants  in  question  occur.  At  the  time 
when  they  were  deposited  the  sea  flowed  up  the  Ottawa 
valley  to  a  height  of  200  to  400  feet  above  its  present 
level,  and  the  valley  of  the  St.  Lawrence  was  a  wide  arm 
of  the  sea,  open  to  the  arctic  current.  Under  these  con- 
ditions the  immense  quantities  of  drift-ice  from  the 
northward,  and  the  removal  of  the  great  heating  surface 
now  presented  by  the  low  lands  of  Canada  and  New  Eng- 
land, must  have  given  for  the  Ottawa  coast  of  that  period 
a  summer  temperature  very  similar  to  that  at  present  ex- 
perienced on  the  Labrador  coast,  and  with  this  conclusion 
the  marine  remains  of  the  Leda  clay,  as  well  as  the  few 


232 


THE  GEOLOGICAL  HISTORY  OF  PLANTi 


lij 


(  I 


land  molluscs  whose  shells  have  been  found  in  the  beds 
containing  the  plants,  and  which  are  species  still  occur- 
ring in  Canada,  perfectly  coincide. 

The  climate  of  that  portion  of  Canada  above  water  at 
the  time  when  these  plants  were  imbedded  may  safely  be 
assumed  to  have  been  colder  in  summer  than  at  present, 
to  an  extent  equal  to  about  5°  of  latitude,  and  this  re- 
frigeiation  may  be  assumed  to  correspond  with  the  re- 
quirements of  the  actual  geographical  changes  implied. 
In  other  words,  if  Canada  was  submerged  until  the 
Ottawa  valley  was  converted  into  an  estuary  inhabited  by 
species  of  Leda,  and  frequented  by  capelin,  the  diminu- 
tion of  the  summer  heat  consequent  on  such  depression 
would  be  precisely  suitable  to  the  plants  occurring  in 
these  deposits,  without  assuming  any  other  cause  of 
change  of  climate. 

I  have  arranged  elsewhere  the  Post-pliocene  deposits 
of  the  central  part  of  Canada,  as  consisting  of,  in  ascend- 
ing order  :  (1)  The  boulder  clay  ;  (2)  a  deep-water  de- 
posit, the  Leda  clay  ;  and  (3)  a  shallow-water  deposit,  the 
Saxicava  sand.  But,  although  I  have  placed  the  boulder 
clay  in  the  lowes.  position,  it  must  be  observed  that  I  do 
not  regard  this  as  a  continuous  layer  of  equal  age  in  all 
places.  On  the  contrary,  though  locally,  as  at  Montreal, 
under  the  Leda  clay,  it  is  in  other  places  and  at  other 
levels  contemporaneous  with  or  newer  than  that  deposit, 
which  itself  also  locally  contains  boulders. 

At  Green's  Creek  the  plant-bearing  nodules  occur  in 
the  lower  part  of  the  Leda  clay,  which  contains  a  few 
boulders,  and  is  apparently  in  places  overlaid  by  large 
boulders,  while  no  distinct  boulder  clav  underlies  it. 
The  circumstances  which  accumulated  the  thick  bed  of 
boulder  clay  near  Montreal  were  probably  absent  in  the 
Ottawa  valley.  In  any  case  we  must  regard  the  deposits 
of  Green's  Creek  as  coeval  with  the  Leda  clay  of  Montreal, 
and  with  the  period  of  the  greatest  abundance  of  Leda 


THE  TERTIARY  TO  THE  MODERN  PERIOD. 


233 


glacialis,  the  most  exclusively  arctic  shell  of  these  de- 
posits. In  other  words,  I  regard  the  plants  above  men- 
tioned as  probably  belonging  to  the  period  of  greatest  re- 
frigeration of  which  we  have  any  evidence,  of  course  not 
including  that  mythical  period  of  universal  incasement  in 
ice,  of  which,  as  I  have  elsewhere  endeavoured  to  show, 
in  so  far  as  Canada  is  concerned,  there  is  no  evidence 
whatever.* 

The  facts  above  stated  in  reference  to  Post-pliocene 
plants  concur,  with  all  the  other  evidence  I  have  been 
able  to  obtain,  in  the  conclusion  that  the  refrigeration  of 
Canada  in  the  Post-pliocene  period  consisted  of  a  diminu- 
tion of  the  summer  heat,  and  was  of  no  greater  amount 
than  that  fairly  attributable  to  the  great  depression  of  the 
land  and  the  different  distribution  of  the  ice-bearing 
arctic  current. 

In  connection  with  the  plants  above  noticed,  it  is  in- 
teresting to  observe  that  at  Green's  Creek,  at  Pakenham 
Mills,  at  Montreal,  and  at  Clarenceville  on  Lake  Cham- 
plain,  species  of  Canadian  Puhnonata  have  been  found  in 
deposits  of  the  same  age  with  those  containing  the  plants. 
The  species  which  have  been  noticed  belong  to  the  genera 
Lymnea  and  Planorhis. 

The  Glacial  age  was,  fortunately,  not  of  very  long  du- 
ration, though  its  length  has  been  much  exaggerated  by 
certain  schools  of  geologists,  f  It  passed  away,  and  a  re- 
turning cosmic  spring  gladdened  the  earth,  and  was  ush- 
ered in  by  a  time  of  great  rainfall  and  consequent  denu- 
dation and  deposit,  which  has  been  styled  the  '*  Pluvial 
Period."  The  remains  of  the  Pliocene  forests  then  re- 
turned— with  somewhat  diminished  numbers  of  species — 


*  Notes  on  Post-Pliocene  of  Canada,  "  Canadian  Naturalist,"  1872. 

f  This  I  have  long  maintained  on  grounds  connected  with  Pleistocene 
fossils,  amount  of  denudation  and  deposit,  &c.,  and  I  am  glad  to  see  that 
Prestwich,  the  best  English  authority  on  such  subjects,  has  recently  an- 
nounced similar  conclusions,  based  on  independent  reasons. 


231 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


from  the  south  and  again  occupied  the  land,  though  they 
have  not  been  able,  in  their  decimated  condition,  to  re- 
store the  exuberance  of  the  flora  of  the  earlier  Tertiary. 
In  point  of  fact,  as  we  shall  see  in  the  next  chapter,  it  is 
the  floras  originating  within  the  polar  circle  and  coming 
down  from  the  north  that  are  rich  and  copious.  Those 
that,  after  periods  of  cold  or  submergence,  return  from 
the  south,  are  comparatively  poor.  Hence  the  modern 
flora  is  far  inferior  to  that  of  the  Middle  Kainozoic.  In 
America,  however,  and  in  eastern  Asia,  for  reasons  al- 
ready stated,  the  return  was  more  abundant  than  in 
Europe. 

Simultaneously  with  the  return  of  the  old  temperate 
flora,  the  arctic  plants  that  had  overspread  the  land  re- 
treated to  mountain-tops,  now  bared  of  ice  and  snow,  and 
back  to  the  polar  lands  whence  they  came  ;  and  so  it  hap- 
pens that,  on  the  White  Mountains,  the  Alps,  and  the 
Himalayas,  we  have  insular  patches  of  the  same  groups  of 
plants  that  exist  around  the  pole. 

These  changes  need  not  have  required  a  very  long 
time,  for  the  multiplication  and  migration  of  plants  are 
very  rapid,  especially  when  aided  by  the  agency  of  migra- 
tory animals.  Many  parts  of  the  land  must,  indeed,  have 
been  stocked  with  plants  from  various  sources,  and  by 
agencies — as  that  of  the  sea — which  might  at  first  sight 
seem  adverse  to  their  distribution.  The  British  Islands, 
for  example,  have  no  indigenous  plants.  Their  flora 
consists  mainly  of  Germanic  plants,  which  must  have 
migrated  to  Britain  in  that  very  late  period  of  the  Post- 
glacial when  the  space  now  occupied  by  the  North  Sea 
was  mostly  dry  land.  Other  portions  of  it  are  Scandi- 
navian plants,  perhaps  survivors  of  the  Glacial  age,  or 
carried  by  migratory  birds ;  and  still  another  element 
consists  of  Spanish  plants,  brought  north  by  spring  mi- 
grants, and  establishing  themselves  in  warm  and  sheltered 
spots,  just  as  the  arctic  plants  do  on  the  bleak  hill-tops. 


THE  TERTIARY   TO  THE   MODERN   PERIOD. 


235 


The  Bermudas,  altogether  recent  islands,  have  one  hun- 
dred and  fifty  species  of  native  plants,  all  of  which  are 
West  Indian  and  American,  and  must  have  been  intro- 
duced by  the  sea-currents  or  by  migratory  birds. 

And  so  the  earth  became  fitted  for  the  residence  of 
modern  man.  Yet  it  is  not  so  good  or  Edenic  a  world  as 
it  once  was,  or  as  it  may  yet  become,  were  another  revo- 
lution to  restore  a  mild  climate  to  the  arctic  regions,  and 
to  send  down  a  new  swarm  of  migratory  species  to  renew 
the  face  of  the  earth  and  restore  it  to  its  pristine  fertility 
of  vegetable  life. 

Thus  closes  this  long  history  of  the  succession  of 
plants,  reaching  from  the  far  back  Laurentian  to  the 
pret.'^nt  day.  It  has,  no  doubt,  many  breaks,  and  much 
remains  to  be  discovered.  Yet  it  may  lead  us  to  some 
positive  conclusions  regarding  the  laws  of  the  introduction 
of  plants. 

One  of  these,  and  perhaps  the  most  remarkable  of  all, 
is  that  certain  prmciples  were  settled  very  far  back,  and 
have  remained  ever  since.  We  have  seen  that  in  the 
earliest  geological  periods  all  that  pertains  to  the  struct- 
ure, powers,  and  laws  of  the  vegetable  cell  was  already 
fixed  and  settled.  When  we  consider  how  much  this 
implies  of  mechanical  structure  and  chemical  and  vital 
property,  the  profound  significance  of  this  statement  be- 
comes apparent.  The  relations  in  these  respects  between 
the  living  cell  and  the  soil,  the  atmosphere  and  the  sun- 
shine, were  apparently  as  perfect  in  the  early  Palaeozoic 
as  in  any  subsequent  time.  The  same  may  be  said  of  the 
structures  of  the  leaf  and  of  the  stem.  In  such  old  forms 
as  Nematophyton  these  were,  it  is  true,  peculiar  and  rudi- 
mentary, but  in  the  Devonian  and  Carboniferous  the 
structure  of  leaves  and  stems  embodied  all  the  parts  and 
principles  that  we  find  at  present.  In  regard  to  fructifi- 
cation there  has  been  more  progress,  for,  so  far  as  we 
know,  the  highest  and  most  complex  forms  of  flowery. 


f 


236 


THE  GEOLOGICAL  HISTORY  OF   PLANTS. 


fruits,  and  seeds  belong  to  the  more  recent  periods,  and 
simpler  forms  were  at  least  dominant  in  the  older  times. 
Yet  even  in  this  respect  the  great  leading  laws  and  struct- 
ures of  bisexual  reproduction  were  perfected  in  the  early 
Pala)ozoic,  and  the  improvements  introduced  in  the  gym- 
nosperm  and  the  angiosperm  of  later  periods  have  con- 
sisted mainly  in  additions  of  accessory  parts,  and  in  modi- 
fications and  refinements  suited  to  the  wants  of  the  higher 
and  more  complex  types. 


I 


'r 


CHAPTER  VIII. 

GENERAL  LAWS  OF  ORIGIN  AND  MIGRATIONS   OF   PLANTS. 
— RELATIONS   OF   RECENT   AND    FOSSIL   FLORAS. 

The  origination  of  the  successive  floras  which  have 
occupied  the  northern  hemisphere  in  geological  time, 
not,  as  one  might  at  first  sight  suppose,  in  the  sunny 
climes  of  the  south,  but  under  the  arctic  skies,  is  a  fact 
long  known  or  suspected.  It  is  proved  by  the  occurrence 
of  fossil  plants  in  Greenland,  in  Spitzbergen,  and  in  Grin- 
nell  Land,  under  circumstances  which  show  that  these 
were  their  primal  homes.  The  fact  bristles  with  physical 
difficulties,  yet  is  fertile  of  the  most  interesting  theoreti- 
cal deductions,  to  reach  which  we  may  well  be  content  to 
wade  through  some  intricate  questions.  Though  not  at 
all  a  new  fact,  its  full  significance  seems  only  recently  to 
have  dawned  on  the  minds  of  geologists,  and  within  the 
last  few  years  it  has  produced  a  number  of  memoirs  and 
addresses  to  learned  societies,  besides  many  less  formal 
notices.* 

The  earliest  suggestion  on  the  subject  known  to  the 
■writer  is  that  of  Prof.  Asa  Gray,  in  1867,  with  reference 
to  the  probable  northern  source  of  the  related  floras  of 
North  America  and  eastern  Asia.  With  the  aid  of  the 
new  facts  disclosed  by  Heer  and  Lesquereux,  Gray  re- 


*  Saporta,  "Ancienne  Vegetation  Polaire";  Hooker,  "Presidential 
Address  to  Royal  Society,"  1818;  Thistleton  Dyer,  "Lecture  on  Plant 
Distribution";  Mr.  Starkie  Gardner,  "Letters  in  'Nature,'"  1878,  &c. 
The  basis  of  most  of  these  brochures  is  to  be  found  in  Heer's  "  Flora 
Fossilis  Arctica." 
22 


238 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


i  <i''-\ 


:;!  i  i  I  'I 


; 


ft 


■ 


turned  to  the  p abject  ir  1872,  and  more  fully  developed 
this  conclusion  with  reference  to  the  Tertiary  floras,* 
and  he  has  recently  still  further  discussed  these  questions 
in  an  able  lecture  on  **  Forest  Geography  and  Archaeol- 
ogy." f  In  this  he  puts  the  case  so  well  and  tersely  that 
we  may  quote  the  following  sentences  as  a  text  for  what 
follows  : 

*'I  can  only  say,  at  large,  that  the  same  species  (of 
Tertiary  fossil  plants)  have  been  found  all  round  the 
world  ;  that  the  richest  and  most  extensive  finds  are  in 
Greenland  ;  that  they  comprise  most  of  the  sorts  which  I 
have  spoken  of,  as  American  trees  which  once  lived  in 
Europe — magnolias,  sassafras,  hickories,  gum-trees,  our 
identical  southern  cypress  (for  all  we  can  see  of  dilfer- 
ence),  and  especially  Sequoias,  not  only  the  two  which 
obviously  answer  to  the  two  big-trees  now  peculiar  to 
California,  but  several  others  ;  that  they  equally  com- 
prise trees  now  peculiar  to  Japan  and  China,  three  kinds 
of  gingko-trees,  for  instance,  one  of  them  not  evidently 
distinguishable  from  tiie  Japan  species  which  alone  sur- 
vives ;  that  we  have  evidence,  not  merely  of  pines  and 
maples,  poplars,  birches,  lindens,  and  whatever  else  char- 
acterise the  temperate  zone  forests  of  our  era,  but  also  of 
particular  species  of  these,  so  like  those  of  our  own  time 
and  country  that  we  may  fairly  reckon  them  as  the  an- 
cestors of  several  of  ours.  Long  genealogies  always  deal 
more  or  less  in  conjecture  ;  but  we  appear  to  be  within 
the  limits  of  scientiiic  inference  when  we  announce  that 
our  existing  temperate  trees  came  from  the  north,  and 
\  thin  tiie  bounds  of  nigh  probability  when  we  claim  not 
a  few  of  them  as  the  originals  of  present  species.  Remains 
of  the  same  plants  have  been  found  fossil  in  our  tem- 
perate region  as  well  as  in  Europe." 


*  Address  to  Atnericar  Associatittn. 

f  "American  Journal  of  Huicuce,"  xvi.,  1878. 


m  I 


GENERAL   LAWS  OF  ORIGIN   AND   MIGRATION.       239 


Between  18G0  and  1870  the  writer  was  engaged  in 
working  out  all  that  could  be  learned  of  the  Devonian 
plants  of  eastern  America,  the  oldest  known  tlora  of  any 
richness,  and  which  consists  almost  exclusively  of  gigantic, 
and  to  us  grotesque,  representatives  of  the  club-mosses, 
ferns,  and  mares'-tails,  with  some  trees  allied  to  the  cycads 
and  pines.  In  this  pursuit  nearly  all  the  more  important 
localities  were  visited,  and  access  was  had  to  the  large 
collections  of  Prof.  Hull  and  Prof.  Newberry,  in  New 
York  and  Ohio,  and  to  those  made  in  the  remarkable 
plant-bearing  beds  of  New  Brunswick  by  Messrs.  Matthew 
and  Hartt.  In  the  progress  of  these  researches,  which 
developed  an  unexpectedly  rich  assemblage  of  species,  the 
northern  origin  of  this  old  flora  seemed  to  be  established 
by  its  earlier  culmination  in  the  northeast,  in  connection 
with  the  growth  of  the  American  land  to  the  southward, 
which  took  place  after  the  great  Upper  Silurian  subsi- 
dence, by  elevations  beginning  in  the  north  while  those 
portions  of  the  continent  to  the  southwest  still  remained 
under  the  sea.  The  same  result  was  indicated  by  the 
persistence  in  the  Carboniferous  of  the  south  and  west  of 
old  Erian  forms,  like  Mef/nlopierin. 

When,  in  1870,  the  labours  of  those  ten  years  were 
brought  before  the  Royal  Society  of  London,  in  the 
Bakerian  lecture  of  that  year,  and  in  a  memoir  illustrat- 
ing  no  less  tiiah  one  hundred  and  twenty-five  species  of 
plants  older  than  the  great  Carboniferous  system,  these 
deductions  were  stated  in  connection  with  the  conclusions 
of  Hull,  Logan,  and  Dana,  as  to  the  distribution  of  sedi- 
ment along  the  northeast  side  of  the  American  continent, 
and  the  anticipation  was  hazarded  that  the  oldest  Palajo- 
zoic  floras  would  be  discovered  to  the  north  of  Newfound- 
land. Mention  was  also  made  of  the  apjjarent  earlier 
and  more  copious  birth  of  the  Devonian  flora  in  America 
than  in  Europe,  a  fact  which  is  itself  connected  with  the 
greater  northward  extension  of  this  continent. 


240 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


II 


The  memoir  containing  these  results  was  not  published 
by  the  Royal  Society,  but  its  publication  was  secured  in  a 
less  complete  form  in  the  reports  of  the  "Geological  Sur- 
vey of  Canada. "  The  part  of  the  memoir  relating  to  Cana- 
dian fossil  plants,  with  a  portion  of  the  theoretical  deduc- 
tions, was  published  in  a  report  issued  in  1871.*  In  this 
report  the  following  language  was  used  : 

"In  eastern  America,  from  the  Carboniferous  period 
onward,  the  centre  of  plant  distribution  has  been  the  Ap- 
palachian chain.  From  this  the  plants  and  sediments 
extended  westward  in  times  of  elevation,  and  to  this  they 
receded  in  times  of  depression.  But  this  centre  was  non- 
existent before  the  Devonian  period,  and  the  centre  for 
this  must  have  been  to  the  northeast,  whence  the  great 
mass  of  older  Appalachian  sediment  was  derived.  In  the 
Carboniferous  period  there  was  also  an  eastward  distribu- 
tion from  the  Appalachians,  and  links  of  connection  in 
the  Atlantic  bed  between  the  floras  of  Europe  and  Ameri- 
ca. In  the  Devonian  such  connection  can  have  been  only 
far  to  the  northeast.  It  is  therefore  in  Newfoundland, 
Labrador,  and  Greenland  that  we  are  to  look  for  the 
oldest  American  flora,  and  in  like  manner  on  the  border 
of  the  old  Scandinavian  nucleus  for  that  of  Europe. 

"Again,  it  must  have  been  the  wide  extension  of  the 
sea  of  the  corniferous  limestone  that  gave  the  last  blow 
to  the  remaining  flora  of  the  Lower  Devonian  ;  and  the 
re-elevation  in  the  middle  of  that  epoch  brought  in  the 
Appalachian  ridges  as  a  new  centre,  and  established  a 
connection  with  Europe  which  introduced  the  Upper 
Devonian  and  Carboniferous  floras.  Lastly,  from  the 
comparative  richness  of  the  later  Erian  f  flora  in  eastern 
America,  especially  in  the  St.  John  beds,  it  might  be  a 

*  '*  Fossil  Plants  of  the  Devonian  and  Upper  Silurian  Formations  of 
Canada,"  pp.  92,  twenty  plates,  Montreal,  1871. 
t  See  pages  lOV  and  108. 


GENERAL  LAWS  OF  ORIGIN  AND   MIGRATION.      241 

fair  inference  that  the  northeastern  end  of  the  Appala- 
chian ridge  was  the  original  birthplace  or  centre  of  crea- 
tion of  what  we  may  call  the  later  Palaeozoic  flora,  or  of 
a  large  part  of  that  flora." 

When  my  paper  was  written  1  had  not  seen  the  ac- 
count i^ublished  by  the  able  Swiss  palseobotanist  Heer,  of 
the  remarkable  Devonian  flora  of  Bear  \sland,  near  Spitz- 
bergen.*  From  want  of  acquaintance  with  the  older 
floras  of  America  and  western  Europe,  Ileer  fell  into  the 
unfortunate  error  of  regarding  the  whole  of  Bear  Island 
plants  as  Lower  Carboniferous,  a  mistake  which  his  great 
authority  has  tended  to  perpetuate,  and  which  has  even 
led  to  the  still  graver  error  of  some  European  geologists, 
who  do  not  hesitate  to  regard  as  Carboniferous  the  fossil 
plants  of  the  American  deposits  from  the  Hamilton  to 
the  Chemung  groups  inclusive,  though  these  belong  to 
formations  underlying  the  oldest  Carboniferous,  and  char- 
acterised by  animal  remains  of  unquestioned  Devonian 
age.  In  1872  I  addressed  a  note  to  the  Geological  Society 
of  London  on  the  subject  of  the  so-called  "  Ursa  stage  '* 
of  Heer,  sliowing  that,  though  it  contained  some  forms 
not  known  at  so  early  a  date  in  temperate  Europe,  it  was 
clearly,  in  part  at  least,  Devonian  when  tested  by  North 
American  standards  ;  but  that  in  this  high  latitude,  in 
which,  for  reasons  stated  in  the  report  above  referred  to, 
I  believed  the  Devonian  plants  to  have  >  riginated,  there 
might  be  an  intermixture  of  the  two  floras.  But  such  a 
mixed  group  should  in  that  latitude  be  referred  to  a 
lower  horizon  than  if  found  in  temperate  regions.  Dr. 
Nathorst,  as  already  stated,  has  recently  obtained  new 
facts  which  go  to  show  that  plants  of  two  distinct  hori- 
zons may  have  been  intermixed  in  the  collections  sub- 
mitted to  Heer. 


*  "Transactions  of  the  Swedish  Academy,"  1871 ;  "Journal  of  the 
London  Geological  Society,"  vol.  xxviii. 


242 


TDE  GEOLOGICAL  HISTORY  OF  PLANTS. 


rsif 


>'      ! 


Between  1870  and  1873  my  attention  was  turned  to 
the  two  subfloras  intermediate  between  those  of  tiie  Devo- 
nian and  the  coal-formation,  the  floras  of  the  Lower 
Carboniferous  (Subcarboniferous  of  some  American  geol- 
ogists) and  the  Millstone  Grit,  and  in  a  report  upon 
these*  similar  deductions  were  expressed.  It  was  stated 
that  in  Newfoundland  the  coal-beds  seem  to  belong  to 
tlic  Millstone  Grit  series,  and  as  we  proceed  southward 
they  belong  to  progressively  newer  portions  of  the  Car- 
boniferous system.  The  same  fact  is  observed  in  the 
coal-beds  of  Scotland,  as  compared  with  those  of  Eng- 
land, and  it  indicates  that  the  coal-formation  flora,  like 
that  of  the  Devonian,  spread  itself  from  the  north,  and 
this  accords  with  the  somewhat  extensive  occurrence  of 
Lower  Carboniferous  rocks  and  fossils  in  the  Parry  Islands 
and  elsewhere  in  the  arctic  regions. 

Passing  over  the  comparatively  poor  flora  of  the  earlier 
Mesozoic,  consisting  largely  of  cycads,  pines,  and  ferns, 
and  as  yet  little  known  in  the  arctic,  and  which  may 
have  originated  in  the  south,  though  represented,  accord- 
ing lu  Ilccr,  by  the  supposed  Jurassic  flora  of  Siberia,  we 
find,  especially  at  Kome  and  Atane  in  Greenland,  an  in- 
teresting occurrence  of  those  earliest  precursors  of  the 
truly  modern  forms  of  plants  which  appear  in  the  Creta- 
ceous, the  period  of  the  English  chalk  and  of  the  New 
Jersey  greensands.  There  are  two  plant-groups  of  this 
age  in  Greenland  ;  one,  that  of  Kome,  consists  almost  en- 
tirely of  ferns,  cycads,  and  pines,  and  is  of  decidedly 
Mesozoic  aspect.  This  is  called  Lower  Cretaceous.  The 
other,  that  of  Atane,  holds  remains  of  many  modern  tem- 
perate genera,  as  Popvlus,  Mi/n'ra,  Ficus,  Sassafras,  and 
Magnolia.  This  is  regarded  as  Upper  Cretaceous.  Rest- 
ing upon  these  Upper  Cretaceous  beds,  without  the  inter- 

*  "Fossil  Plants  of  Lower  Carboniferous  and  ^lillstone  Grit  Forma- 
tions of  Canada, '  pp.  47,  ten  plates,  Montreal,  1S73.  


i:    ! 


"\\\\ 


GENERAL   LAWS  OF  ORIGIN   AND  MIGRATION.      243 

vention  of  any  other  formation,*  are  beds  rich  in  plants 
of  much  more  modern  appearance,  and  referred  by  Ileer 
to  the  Miocene  period,  a  reference,  as  we  have  seen,  not 
Wf.rranted  by  comparison  with  the  Tertiary  plants  of  Eu- 
rope or  of  America.  Still  farther  north  this  so-called 
Miocene  assemblage  of  plants  appears  in  Spitzbergen  and 
Grinnell  Land  ;  but  there,  owing  to  the  predominance  of 
trees  allied  to  the  spruces,  it  has  a  decidedly  more  boreal 
character  than  in  Greenland,  as  might  be  anticipated  from 
its  nearer  approach  to  the  pole.f 

If  now  we  turn  to  the  Cretaceous  and  Tertiary  floras 
of  western  America,  as  described  by  Lesquereux,  New- 
berry, and  others,  we  find  in  the  lowest  Cretaceous  rocks 
there  known — those  of  the  Dakota  group — which  may  be 
in  the  lower  part  of  the  Middle  Cretaceous,  a  series  of 
plants  J  essentially  similar  to  those  of  the  so-called  Upper 
Cretaceous  of  Greenland.  They  occur  in  beds  indicating 
land  and  fresh-water  conditions  as  prevalent  at  the  time 
over  great  areas  of  the  interior  of  America.  But  over- 
lying this  plant-bearing  formation  we  have  an  oceanic 
limestone  (the  Niobrara),  corresponding  in  many  respects 
to  the  European  chalk,  and  extending  far  north  into  the 
British  territory,*  indicating  that  the  land  of  the  Lower 
Cretaceous  was  replaced  by  a  vast  Mediterranean  Sea, 
filled  with  warm  water  from  the  equatorial  currents,  and 
not  invaded  by  cold  waters  from  the  north.  This  is  suc- 
ceeded by  thick  Upper  Cretaceous  deposits  of  clay  and 
sandstone,   with  marine  remains,   though   very  sparsely 


*  Nordenskiold,  "  Expedition  to  Greenland,"  "  Geological  Magazine," 
1872. 

f  Yet  even  here  the  bald  cypress  {Taxodium  dis/lchum),  or  a  tree 
nearly  allied  to  it,  is  found,  though  this  species  is  now  limited  to  the 
Southern  States.  Ficldcu  and  De  Ranee,  "  Journal  of  the  Geological  So- 
ciety," 1878. 

1(.  Lesquereux,  "  Report  on  Cretaccoiis  Flora." 

**  G.  M.  Dawson,  "  Report  on  Forty-ninth  Parallel" 


244 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


ml 


distributed  ;  and  these  show  that  further  subsidence  or 
denudation  in  the  north  had  opened  a  way  for  the  arctic 
currents,  killing  out  the  warm-water  animals  of  the  Nio- 
brara group,  and  filling  up  the  Mediterranean  of  that 
period.  Of  the  flori*  of  these  Upper  Cretaceous  periods, 
which  must  have  been  very  long,  we  know  something  in 
the  interior  regions,  from  the  discovery  of  a  somewhat  , 
rich  flora  in  the  Dunvegan  beds  of  the  Peace  River  dis- 
trict, on  the  northern  shore  of  the  great  Cretaceous  Medi- 
terranean;* and  on  the  coast  of  British  Columbia  we 
have  the  remarkable  Cretaceous  coal-field  of  Vancouver 
Island,  which  holds  the  remains  of  plants  of  modern 
genera,  and,  indeed,  of  almost  as  modern  aspect  as  those 
of  the  so-called  Miocene  of  Greenland.  They  indicate, 
however,  a  warmer  climate  as  then  prevalent  on  the  Pa- 
cific coast,  and  in  this  respect  correspond  with  a  peculiar 
transition  flora,  intermediate  between  the  Cretaceous  and 
Eocene  or  earliest  Tertiary  of  the  interior  regions,  and 
which  is  described  by  Lesquereux  as  the  Lower  Lig- 
nitic. 

Immediately  above  these  Upper  Cretaceous  beds  we 
have  the  great  Lignite  Tertiary  of  the  West — the  Laramie 
group  of  recent  American  reports — abounding  in  fossil 
plants,  at  one  time  regarded  as  Miocene,  but  now  known 
to  be  Lower  Eocene,  though  farther  south  extending  up- 
ward toward  the  Miocene  age.f  These  beds,  with  their 
characteristic  plants,  have  been  traced  into  the  British 
territory  north  of  the  forty-ninth  parallel,  and  it  has  been 
shown  that  their  fossils  are  identical  with  those  of  the 

*  "  Reports  of  Dr.  G.  M.  Dawson,  Geological  Survey  of  Canada."  Also, 
"  Transactions  of  the  Royal  Society  of  Canada,"  vol.  i. 

f  Lesquereux's  "  Tertiary  Flora  " ;  "  White  on  tlic  Lar<imie  Group  "  ; 
Stevenson,  "Geological  Relations  of  Lignitic  Groups,"  American  Philo- 
sophical Society,  June,  1875;  Dawson,  "Transactions  of  the  Royal  So- 
ciety of  Canada,"  vol.  iv. ;  Ward,  "  Bulletin  of  United  States  Geological 
Survey." 


i 


GENERAL  LAWS  OF  ORIGIN  AND  MIGRATION.       245 


Also, 


McKenzie  River  valley,  described  by  Heer  as  Miocene, 
and  probably  also  with  those  of  Alaska,  referred  to  the 
same  age.*  Now  this  truly  Eocene  flora  of  the  temperate 
and  northern  parts  of  America  has  so  many  species  in 
common  with  that  called  Miocene  in  Greenland  that  its 
identity  can  scarcely  be  doubted.  These  facts  have  led 
to  scepticism  as  to  the  Miocene  age  of  the  upper  plant- 
bearing  beds  of  Greenland,  and  more  especially  Mr.  J. 
Starkie  Gardner  has  ably  argued,  from  comparison  with 
the  Eocene  flora  of  England  and  other  considerations, 
that  they  are  really  of  that  earlier  date,  f 

In  looking  at  this  question,  we  may  fairly  assume  that 
no  climate,  however  equable,  could  permit  the  vegeta- 
tion of  the  neighbourhood  of  Disco  in  Greenland  to  be 
exactly  identical  with  that  of  Colorado  and  Missouri,  at  a 
time  when  little  difl!erence  of  level  existed  in  the  two 
regions.  Either  the  southern  flora  migrated  ^  ch  in 
consequence  of  a  greater  amelioration  of  climate-,  or  the 
northern  flora  moved  southward  as  the  climate  became 
colder.  The  same  argument,  as  Gardner  has  ably  shown, 
applies  to  the  similarity  of  the  Tertiary  plants  of  temper- 
ate Europe  to  those  of  Greenland.  If  Greenland  required 
a  temperature  of  about  50°,  as  Ileer  calculates,  to  main- 
tain its  Eocene  flora,  the  temperature  of  England  and 
that  of  the  Southwestern  States  must  have  been  higher, 
though  probably  more  equable,  than  at  present. 

We  cannot  certainly  affirm  anything  respecting  the 
migrations  of  these  floras,  but  there  are  some  probabilities 
which  deserve  attention.  The  ferns  and  cycads  of  the 
so-called  Lower  Cretaceous  of  Greenland  are  nothing  but 
a  continuation  of  the  previous  Jurassic  flora.  Now  this 
was  established  at  an  equally  early  date  in  the  Queen 


*  G.  M.  Dawson,  "  Report  on  the  Geology  of  the  Forty-ninth  Parallel," 
whore  full  details  on  these  points  may  be  found.  "  Transactions  of  the 
Royal  Society  of  Canada,"  vol.  iv. 

f  "Nature,"  December  12,  1H78. 


I 


in 


■■      ':  Hi 

!i| 

r  IT' 


(I 


r  i   • 


II  f{  i  ;» 


|i  ' 


246 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


Charlotte  Islands,*  and  still  earlier  in  Virginia,  f  The 
presumption  is,  therefore,  that  it  came  from  the  south. 
It  has,  indeed,  the  facies  of  a  southern  hemisphere  and 
insular  flora,  and  probably  spread  itself  northward  as  far 
as  Greenland,  at  a  time  when  our  northern  continents 
were  groups  of  islands,  and  when  the  ocean  currents  were 
carrying  warm  water  far  toward  the  arctic  regions.  The 
flora  which  succeeds  this  in  the  sections  at  Atane  has  no 
special  affinities  with  the  southern  hemisphere,  and  is  of 
a  more  temperate  and  continental  character.  |  It  is  not 
necessarily  Upper  Cretaceous,  since  it  is  similar  to  that 
of  the  Dakota  group  farther  south,  and  this  is  at  least 
Middle  Cretaceous.  This  flora  must  have  originated 
either  somewhere  in  temperate  America  or  within  the 
Arctic  circle,  and  it  musi;  have  replaced  the  older  one  by 
virtue  of  increasing  coolness  and  continental  character  of 
climate.  It  must,  therefore,  have  been  connected  with 
that  elevation  of  the  land  which  took  place  at  the  begin- 
ning of  the  Cretaceous.  During  this  elevation  it  spread 
over  all  western  America  at  one  time  or  another,  and,  as 
the  land  again  subsided  under  the  sea  of  the  Niobrara 
chalk,  it  assumed  an  aspect  more  suited  to  a  warm  cli- 
mate, but  still  held  its  place  on  such  islands  as  remained 
above  water  along  the  Pacific  coast  and  in  the  north,  and 
it  continued  to  exist  on  these  islands  till  the  colder  seas 

*  "  Reports  of  the  Geological  Survey  of  Canada." 

f  Fontaine  has  well  described  the  ^lesozoic  flora  of  Virginia,  "  Ameri- 
can Journal  of  Science,"  January,  18V9,  and  "  Report  on  Early  Mesozoic 
Floras." 

X  In  the  "  Proceedings  of  the  Royal  Society  of  Tasmania,"  1887,  Mr. 
R.  M.  Johnston,  F.  L.  S.,  states  that  in  the  Miocene  beds  of  Tasmania  trees 
of  European  genera  abound.  The  Mesozoic  flora  of  that  island  is  of  the 
usual  conifero-cycadean  type.  Ettingshausen  makes  a  similar  statement 
in  the  "  Geological  Magazine  "  respecting  the  Tertiary  flora  of  Australia 
and  New  Zealand,  stating  that,  like  the  Tertiary  floras  of  Europe,  they 
have  a  mixed  character,  being  partly  of  types  now  belonging  to  the  north- 
ern hemisphere. 


GENERAL  LAWS  OF  ORIGIN    AND   MIGRATION.       247 

of  the  Upper  Cretaceous  liad  again  given  place  to  the 
warm  plains  and  land-locked  brackish  seas  or  fresh-water 
lakes  of  the  Laramie  period  (Eocene).  Thus  the  true 
Upper  Cretaceous  marks  a  cool  period  intervening  be- 
tween the  so-called  Upper  Cretaceous  (really  Middle  Cre- 
taceous) and  the  so-called  Miocene  (really  Lower  Eocene) 
floras  of  Greenland. 

This  latter  established  itself  in  Greenland,  and  prob- 
ably all  around  the  Arctic  circle,  in  the  warm  period  of 
the  earliest  Eocene,  and,  as  the  climate  of  the  northern 
hemisphere  became  gradually  reduced  from  that  time  till 
the  end  of  the  Pliocene,  it  marched  on  over  both  conti- 
nents to  the  southward,  chased  behind  by  the  modern 
arctic  flora,  and  eventually  by  the  frost  and  snow  of  the 
Glacial  age.  This  history  may  admit  of  correction  in  de- 
tails ;  but,  so  far  as  present  knowledge  extends,  it  is  in 
the  main  not  far  from  the  truth. 

Perhaps  the  first  great  question  which  it  raises  is  that 
as  to  the  causes  of  the  alternations  of  warm  and  cold  cli- 
mates in  the  north,  apparently  demanded  by  the  vicissi- 
tudes of  the  vegetable  kingdom.  Here  we  may  set  aside 
the  idea  that  in  former  times  plants  were  suited  to  endure 
greater  cold  than  at  present.  It  is  true  that  some  of  the 
fossil  Greenland  plants  are  of  unknown  genera,  and  many 
are  species  new  to  us ;  but  we  are  on  the  whole  safe  in 
affirming  that  they  must  have  required  conditions  similar 
to  those  necessary  to  their  modern  representatives,  except 
within  such  limits  as  we  now  find  to  hold  in  similar  cases 
among  existing  plants.  Still  we  know  that  at  the  present 
time  many  species  found  in  the  equable  climate  of  Eng- 
land will  not  live  in  Canada,  though  species  to  all  appear- 
ance similar  in  structure  are  native  here.  There  is  also 
some  reason  to  suppose  that  species  when  new  may  have 
greater  hardiness  and  adaptability  than  when  in  old  age 
and  verging  toward  extinction.  In  any  case  these  facts 
can  account  for  but  a  small  part  of  the  phenomena,  which 


248 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


'f 


'  f 


1*1 1 


V  '  ■ 


require  to  be  explained  by  physical  changes  affecting  the 
earth  as  a  whole,  or  at  least  the  northern  hemisphere. 
Many  theoretical  views  have  been  suggested  on  this  sub- 
ject, and  perhaps  the  most  practical  way  of  disposing  of 
these  will  be  first  to  set  aside  a  number  which  are  either 
precluded  by  the  known  facts,  incapable  of  producing 
the  effects,  or  altogether  uncertain  as  to  their  possible 
occurrence. 

1.  In  this  class  we  may  place  the  theory  that  the  x^oles 
of  the  earth  have  changed  their  position.  Independently 
of  astronomical  objections,  there  is  good  geological  evi- 
dence that  the  poles  of  the  earth  must  have  been  nearly 
in  their  present  places  from  the  dawn  of  life  until  now. 
From  the  Laurentian  upward,  those  organic  limestones 
which  mark  the  areas  where  warm  and  shallow  equatorial 
water  was  spreading  over  submerged  continents  are  so 
disposed  as  to  prove  the  permanence  of  the  poles.  In 
like  manner  all  the  great  foldings  of  the  crust  of  the  earth 
have  followed  lines  which  are  parts  of  great  circles  tangent 
to  the  existing  polar  circles.  So,  also,  from  the  Cambrian 
age  the  great  drift  of  sediment  from  the  north  has  fol- 
lowed the  line  of  the  existing  Arctic  currents  from  the 
northeast  to  the  southwest,  throwing  itself,  for  example, 
along  the  line  of  the  Appalachian  uplifts  in  eastern 
America,  and  against  the  ridge  of  the  Cordilleras  in  the 
west. 

2.  Some  of  the  above  considerations,  along  with  astro- 
nomical evidence,  prevent  us  from  assuming  any  consid- 
erable change  in  the  obliquity  of  the  axis  of  the  earth 
during  geological  time. 

3.  That  the  earth  and  the  sun  have  diminished  in 
heat  during  geological  time  seems  probable  ;  but  physical 
and  geological  facts  alike  render  it  certain  that  this  influ- 
ence could  have  j)roduced  no  appreciable  effect,  even  in 
the  times  of  the  earliest  floras,  and  certainly  not  in  the 
case  of  Tertiary  vegetation. 


'^m. 


GENERAL   LAWS  OF  ORIGIN  AND   MIGRATION.       O^y 


4.  It  has  boon  supposed  that  the  earth  may  have  at 
different  times  traversed  more  or  less  lieated  zones  of 
space,  giving  alternations  of  warm  and  cold  temperature. 
No  such  differences  in  space  are,  however,  known,  nor 
does  there  seem  any  good  ground  for  imagining  their  ex- 
istence. 

5.  The  heat  of  the  sun  is  known  to  be  variable,  and 
the  eleven  years'  period  of  sun-spots  has  recently  attracted 
much  attention  as  producing  appreciable  effects  on  the 
seasons.  There  may  possibly  be  longer  cycles  of  solar 
energy,  or  the  sun  may  be  liable,  like  some  variable  stars, 
to  paroxysms  of  increased  energy.  Such  changes  are 
possible,  and  may  fairly  be  taken  into  the  account,  pro- 
vided that  we  fail  to  find  known  causes  sufficient  to  ac- 
count for  the  phenomena. 

Of  well-known  causes  there  seem  to  be  but  three. 
These  are  :  First,  that  urged  by  Lyell — viz.,  the  varying 
distribution  of  land  and  water  along  with  that  of  marine 
currents  ;  secondly,  the  varying  eccentricity  of  the  earth's 
orbit,  along  with  the  precession  of  the  equinoxes,  and  the 
effects  of  this  on  oceanic  circulation,  as  illustrated  by 
CroU  ;  thirdly,  the  different  conditions  of  the  earth's 
atmosphere  with  reference  to  radiation,  as  argued  by  Tyn- 
dall  and  Hunt.  As  these  causes  are  all  founded  on  known 
facts,  and  not  exclusive  of  each  other,  Ave  may  consider 
them  together.  1  shall  take  the  Lyellian  theory  first,  re- 
garding it  as  the  most  important,  and  the  best  supported 
by  geological  facts. 

We  know  that  the  present  distribution  of  land  and 
water  greatly  influences  climate,  more  especially  by  af- 
fecting that  of  the  ocean  currents  and  of  the  winds,  and 
by  the  different  action  of  land  as  compared  with  water  in 
the  reception  and  radiation  of  heat.  The  present  distri- 
bution of  land  gives  a  large  predominance  to  the  arctic 
and  sub-arctic  regions,  as  compared  with  the  equatorial 
and  with  the  antarctic  ;  and  we  might  readily  imagine 
23 


;  i 


i  i 


1  'ii 


250 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


otlier  distributioTis  tliat  would  give  very  different  results. 
But  this  i.s  not  an  imaginary  case.  Wo  know  that,  while 
the  forms  and  positions  of  the  great  continents  have  been 
fixed  from  a  very  early  date,  they  have  experienced  many 
great  submergences  and  re-elevations,  and  that  these  have 
occurred  in  somewhat  regular  secjuence,  as  evidenced  by 
the  cyclical  alternations  of  organic  limestones  and  earthy 
sediments  in  successive  geological  formations. 

An  example  bearing  on  our  present  subject  may  servo 
to  illustrate  this.  In  the  latter  part  of  the  Upper  Silu- 
rian period  (the  Lower  llelderberg  age),  vast  areas  of  the 
American  continent*  were  covered  Avith  an  ocean  in 
which  were  deposited  organic  limestones  whose  fossils 
show  that  this  great  interior  sea  was  pervaded  by  equa- 
torial waters  bringing  food  and  warmth,  while  the  in- 
cipient ranges  of  the  Appalachians  on  the  east,  and  the 
Cordilleras  on  the  west,  and  the  Laurentian  axis  on  the 
north,  fenced  off  from  it  the  colder  arctic  waters.  How 
different  must  the  climate  of  America  and  of  the  region 
north  of  it  have  been  in  these  circumstances  from  that 
which  prevails  at  present,  or  from  that  which  prevailed 
in  certain  other  periods,  when  it  was  open  to  the  incur- 
sions of  the  arctic  ice-laden  currents,  bearing  loads  of  fine 
sediment  !  f  It  was  in  these  circumstances,  and  in  the 
similar  circumstances  in  which  the  great  Corniferous 
limestone  of  the  Devonian  was  deposited — a  limestone 
showing  in  its  rich  coral  fauna  even  warmer  waters  than 
those  of  the  Lower  Helderberg — that  the  Devonian  flora 

*  See  a  memoir  and  map  by  Prof.  Hall,  "  Reports  of  the  Regents  of 
New  York,"  18'74-'75.  *     .        .     •     ^    '  : 

f  It  seems  certain  that  the  faunae  of  the  old  limestones,  like  the  Tren- 
ton, Niagara,  Lower  Helderberg,  and  Corniferous,  belong  to  warm  and 
sheltered  sea  areas,  and  that  those  rich  in  graptolites  and  trilobites,  en- 
closed in  muddy  sediments,  belong  to  the  colder  arctic  waters.  Such 
arctic  faunae  are  those  of  the  Quebec  group  and  of  the  Utica  shale,  and 
to  some  extent  that  of  the  Hamilton  group. 


J 


GENERAL  LAWS  OF  ORIGIN   AND   MIGRATION.       251 

took  its  origin  in  the  north  and  advanced  southward  over 
ney  lands  in  process  of  emergence  from  the  sea.  Tho 
somewhat  similar  condition  evidenced  by  the  Lower  Car- 
boniferous limestone  preceded  the  advent  of  the  great  and 
lich  flora  of  the  coal-formation. 

Lyell's  theory  on  this  subject  has,  I  think,  in  some  re- 
cent publications,  been  somewhat  misapprehended.  It 
is  true  that  he  stated  hypothetically  two  contrasted  con- 
ditions of  distribution,  in  one  of  which  all  the  land  was 
equatorial,  in  another  all  polar  ;  but  he  did  not  suppose 
that  these  conditions  had  actually  occurred  ;  and  even  in 
his  earlier  editions,  before  the  recent  discoveries  and  dis- 
cussions as  to  ocean  currents,  he  was  always  careful  to  at- 
tach due  value  to  these  in  connection  with  subsidences 
and  elevations.*  In  his  later  editions  he  introduced 
more  full  references  to  current  action,  and  also  stated 
Croll's  theory,  but  still  maintained  the  validity  of  his 
original  conclusions. 

The  sufficiency  of  this  Lyellian  theory  to  account  for 
the  facts,  in  so  far  as  plants  are  concerned,  may,  I  think, 
be  inferred  from  the  course  of  the  isothermal  lines  at 
present.  The  south  end  of  Greenland  is  on  the  latitude 
of  Christiania  in  Norway  on  the  one  hand,  and  of  Fort 
Liard  in  the  Peace  River  region  on  the  other ;  and  while 
Greenland  is  clad  in  ice  and  snow,  wheat  and  other  grains, 
and  the  ordinary  trees  of  temperate  climates,  grow  at  the 
latter  places. f  It  is  evident,  therefore,  that  only  excep- 
tionally unfavourable  circumstances  prevent  the  Greenland 
area  from  still  possessing  a  temperate  flora,  and  these  un- 
favourable circumstances  possibly  tell  even  on  the  locali- 
ties with  which  we  have  compared  it.  Further,  the 
mouth  of  the  McKenzie  River  is  in  the  same  latitude  with 


*  See  "  Principles  of  Geolofry,"  edition  of  1840,  chapter  vii. 
f  See  "  Macoun's  Report,"  "  Geological  Survey  of  Canada,"  and  Rich- 
ardson's "  Boat  Voyage." 


252 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


Disco,  near  wliich  are  some  of  the  most  celebrated  locali- 
ties of  fossil  Cretaceous  ai)l  Tertiary  plants.  Yet  tho 
mouth  of  the  MoKenzie  River  enjoys  a  much  more  favour- 
able climate  and  has  a  much  more  abundant  flora  than 
Disco.  If  north  Greenland  were  submerged,  and  low 
land  reaching  to  the  south  terminated  at  Disco,  and  if 
from  any  cause  either  the  cold  currents  of  liattin's  Bay 
were  arrested,  or  additional  warm  water  thrown  into  the 
North  Atlantic  by  the  Gulf  Stream,  there  is  nothing  to 
prevent  a  mean  temperature  of  45'"  Fahr.  from  prevailing 
at  Disco  ;  and  the  estimate  ordinarily  formed  of  the  re- 
quirements of  its  extinct  floras  is  50°,*  which  is  probably 
above  rather  than  below  the  actual  temperature  rcfjuired. 

Since,  then,  geological  facts  assure  us  of  mutations  of 
the  continents  much  greater  than  those  apparently  re- 
quired to  account  for  the  clianges  of  climate  implied  in 
the  existence  of  the  ancient  arctic  floras,  it  does  not  seem 
absolutely  necessary  to  invoi<e  any  others. f  If,  however, 
there  are  other  true  causes  which  might  either  aid  or 
counteract  those  above  referred  to,  it  may  be  well  to 
consider  them. 

Mr.  Croll  has,  in  his  valuable  work  ''  Climate  and 
Time,"  and  in  various  memoirs,  brought  forward  an  in- 
genious astronomical  theory  to  account  for  changes  of 
climate.  This  theory,  as  stated  by  himself  in  a  recent 
paper,J  is  that  when  the  eccentricity  of  the  earth's  orbit 
is  1  high  value,  and  the  northern  winter  solstice  is  in 
perihelion,  agencies  are  brought  into  operation  which 
make  the  southeast  trade-winds  stronger  than  the  north- 
east, and  compel  them  to  blow  over  upon  the  nortliern 


*  lloer.  Reo,  also,  papers  by  Prof.  Ilaugliton  and  by  Gardner  in 
"Nature"  for  1878, 

f  Sir  VVilliiun  Thomson,  "  Transactions  of  the  Geological  Society  of 
Glas;,'ow,"  February  22,  1878. 

I  "  C'ataclyfiniic  Theories  of  Geological  Climate,"  "  Geological  Maga- 
zine," May,  1878. 


OENERAL   LAWS   OF  ORIGIN   AND   MIGRATION.       253 


Maga- 


hcmispherc  as  far  as  the  Tropic  of  Cancer.  The  result  is 
that  all  the  <i;rcnt  e(jiiatorial  currents  of  the  ocean  are  im- 
pelled into  the  north  tn  hemisphere,  wliich  thus,  in  con- 
sequence of  thj  immense  accumulation  of  warm  water, 
has  its  temperature  raised,  so  that  ice  and  snow  must  to  a 
great  extent  disappear  from  the  arctic  regions.  In  the 
prevalence  of  the  converse  conditions,  the  arctic  zone  be- 
comes clad  in  ice,  and  the  southern  has  its  temperature 
raised. 

At  the  same  time,  according  to  CroH's  calculations, 
the  accumulation  of  ice  on  either  pole  would  tend,  by 
shifting  the  earth's  centre  of  gravity,  to  raise  the  level  of 
the  ocean  and  submerge  the  land  on  the  colder  hemisphere. 
Thus  a  submergence  of  land  would  coincide  with  a  cold 
condition,  and  emergence  with  increasing  warmth.  Facts 
already  referred  to,  however,  show  that  this  has  not  al- 
ways been  the  case,  but  that  in  many  cases  submergence 
was  accompanied  with  the  influx  of  warm  equatorial 
waters  and  a  raised  temperature,  this  apparently  depend- 
ing on  the  (juestion  of  local  distribution  of  land  and 
water  ;  and  this  in  its  turn  being  regulated  not  always  by 
mere  shiftingof  the  centre  of  gravity,  but  by  foldings  occa- 
sioned by  contraction,  by  equatorial  subsidences  resulting 
from  the  retardation  of  the  earth's  rotation,  and  by  the  ex- 
cess of  material  abstracted  by  ice  and  frost  from  the  arctic 
regions,  and  drifted  southward  along  the  lines  of  arctic 
currents.  This  drifting  must  in  all  geological  times  have 
greatly  exceeded,  as  it  certainly  does  at  present,  the  de- 
nudation caused  by  atmospheric  action  at  the  equator, 
and  must  have  tended  to  increase  the  dispositioii  to  equa- 
torial collapse  occasioned  by  retardation  of  rotation.* 

While  such  considerations  as  those  above  referred  to 

*  Croll,  in  "C'liriiato  ani3  Time,"  and  in  a  note  roarl  before  the  Briti-'h 
AB.sociali()n  in  187»),  takr-s  an  opposite  view;  but  tliis  in  ch-arly  t-ontrary 
to  the  facts  of  hodiiiieiitaliitn,  which  show  a  steady  movcuient  of  debrvi 
toward  the  ijoutli  and  tjouthwest. 


254: 


THE   GEOLOGICAL   HISTORY  OF  PLANTS. 


ii 


:1i 


■it- 


tend  to  reduce  the  practical  importance  of  Mr.  Croll's 
theory,  on  the  other  hand  they  tend  to  remove  one  of  the 
greatest  objections  against  it — namely,  that  founded  on 
the  necessity  of  supposing  that  glacial  periods  recur  with 
astronomical  regularity  in  geological  time.  They  cannot 
do  so  if  dependent  on  other  causes  inherent  in  the  earth 
itself,  and  producing  important  movements  of  its  crust. 

The  third  great  cause  of  warmer  climates  in  the  past 
is  the  larger  proportion  of  carbon  dioxide,  or  carbonic- 
acid  gas,  in  the  atmosphere  in  early  geological  times,  as 
proved  by  the  immense  amount  of  carbon  now  sealed  up  in 
limestone  and  coal,  and  which  must  at  one  time  have  been 
in  the  air.  It  has  been  shown  that  a  very  small  additional 
cpiantity  of  this  substance  would  so  obstruct  radiation  of 
heat  from  the  eartii  as  to  act  almost  like  a  glass  roof.  If, 
however,  the  quantity  of  carbonic  acid,  great  at  first,  was 
slowly  and  regularly  removed,  even  if,  as  suggested  by 
Hunt,  small  additional  supplies  were  gradually  added 
from  space,  this  cause  could  have  affected  only  the  very 
oldest  floras.  But  it  is  known  that  some  comets  and 
meteorites  contain  carbonaceous  matter,  and  this  allows 
us  to  suppose  that  ace  sions  of  carbon  may  have  been 
communicated  at  irregular  intervals.  If  so,  there  may 
have  been  cycles  of  greater  and  less  abundance  of  this 
substance,  and  an  atmosphere  rich  in  carbon  dioxide 
might  at  one  and  the  same  time  afford  warmth  and  abund- 
dance  of  food  to  plants. 

It  thus  appears  that  the  causes  of  ancient  vicissitudes 
of  climate  arc  somewhat  complex,  and  when  two  or  more 
of  them  happened  to  coincide  very  extreme  changes  might 
result,  having  most  important  bearings  on  the  distribu- 
tion of  plants. 

This  may  help  us  to  deal  with  the  eculiaritics  of  the 
great  Glacial  ago,  which  may  have  been  rendered  excep- 
tionally severe  by  the  combination  of  several  of  the  causes 
of  refrigeration.     "We  must  not  suppose,  however,  that 


GENERAL   LAWS   OF  ORIGIN  AND   MIGRATION.       255 


I 


the  views  of  those  extreme  glacialists  who  suppose  conti- 
nental ice-caps  reaching  lialf  way  to  tlie  equator  are  borne 
out  by  facts.  In  truth,  the  ice  accumulating  round  the 
pole  must  have  been  surrounded  by  water,  and  there  must 
have  been  tree-clad  islands  in  the  midst  of  the  icy  seas, 
even  in  the  time  of  greatest  refrigeration.  This  is  proved 
by  the  fact  that,  in  the  Lcda  clay  of  eastern  Canada, 
which  belongs  to  the  time  of  greatest  submergence,  and 
whose  fossil  shells  show  sea-water  almost  at  tlie  freezing- 
point,  there  are  leaves  of  poplars  and  other  plants  wliich 
must  have  been  drifted  from  neighbouring  shores.  Simi- 
lar remains  occur  in  clays  of  like  origin  in  the  basin  of 
the  great  lakes  and  in  the  West.  These  have  been  called 
*'  interglacial,"  but  there  is  no  evidence  to  prove  that  they 
are  not  truly  glacial.  Thus,  while  we  need  not  suppose 
that  plants  existed  within  the  Arctic  circle  in  the  Glacial 
age,  we  have  evidence  that  those  of  the  cold  temperate 
and  sub-arctic  zones  continued  to  exist  pretty  far  north. 
At  the  same  time  the  warm  temperate  flora  would  be 
driven  to  the  south,  excei)t  where  sustained  in  insular 
spots  warmed  by  the  equatorial  currents.  It  would  return 
northward  on  the  re-elevation  of  the  land  and  the  re- 
newal of  warmth. 

If,  however,  our  modern  flora  is  thus  one  that  has  re- 
turned from  the  south,  this  would  account  for  its  poverty 
in  species  as  compared  with  those  of  the  early  Tertiary. 
Groups  of  plants  descending  from  the  north  have  been 
rich  and  varied.  Returning  from  the  south  they  are  like 
the  shattered  remains  of  a  beaten  army.  This,  at  least, 
has  been  the  case  with  such  retreating  floras  as  those  of 
the  Lower  Carboniferous,  the  Permian,  and  the  Jurassic, 
and  possibly  that  of  the  Lower  Eocene  of  Europe. 

The  question  of  the  su;)ply  of  light  to  an  arctic  flora 
is  much  less  difficult  than  some  have  imagined.  The 
long  summer  day  is  in  this  respec^  a  good  substitute  for 
a  longer  season  of  growth,  wliile  a  copious  covering  of 


25G 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


I     !■ 


iilliili 


winter  snow  not  only  protects  evergreen  plants  from  those 
sudden  alternations  of  temperature  which  are  more  de- 
structive than  intense  frost,  and  prevents  the  frost  from 
penetrating  to  their  roots,  but,  by  the  ammonia  which  it 
absorbs,  preserves  their  greenness.  According  to  Dr. 
Brown,  the  Danish  ladies  of  Disco  long  ago  solved  this 
problem.*  Ho  informs  us  that  they  cultivate  in  their 
houses  most  of  our  garden  flowers — as  roses,  fuchsias,  and 
geraniums — showing  that  it  is  merely  warmth  and  not 
light  that  is  required  to  enable  a  subtropical  flora  to 
thrive  in  Greenland.  Even  in  Canada,  which  has  a  flora 
richer  in  some  respects  than  that  of  temperate  Europe, 
growth  is  effectually  arrested  by  cold  for  nearly  six 
months,  and  though  there  is  ample  sunlight  there  is  no 
vegetation.  It  is,  indeed,  not  impossible  that  in  the 
plans  of  the  Creator  the  continuous  summer  sun  of  the 
arctic  regions  may  have  been  made  the  means  for  the  in- 
troduction, or  at  least  for  the  rapid  growtii  and  multipli- 
cation, of  new  and  more  varied  types  of  plants. 

Mucli,  of  course,  remains  to  be  known  of  the  history 
of  the  old  floras,  whose  fortunes  1  have  endeavoured  to 
sketch,  and  which  seem  to  have  been  driven  like  shuttle- 
cocks from  north  to  south,  and  from  south  to  north, 
especially  on  the  American  continent,  whose  meridional 
extension  seems  to  have  given  a  field  si)ecially  suited  for 
such  operations. 

This  great  stretch  of  the  western  continent,  from 
north  to  south,  is  also  connected  with  the  interesting  fact 
that,  when  new  floras  are  entering  from  the  arctic  re- 
gions, they  appear  earlier  in  America  than  in  Europe, 
and  that  in  times  when  old  floras  are  retreating  from  the 
south  old  genera  and  species  linger  longer  in  America. 
Thus,  in  the  Devonian  and  Cretaceous  new  forms  of  those 
periods  appear  in  America  long  before  they  are  recognized 

*  "Florula  Discoana,"  Botanical  Soc'ety  of  Edinburgh,  1868. 


GENERAL  LAWS  OF  ORIGIN  AND   MIGRATION.       257 


"^W 


in  Europe,  and  in  the  modern  epoch  forms  that  would  be 
regarded  in  Europe  as  Miocene  still  exist.  Much  confu- 
sion in  reasoning  as  to  the  geological  ages  of  the  fossil  floras 
has  arisen  from  want  of  attention  to  this  circumstance. 

What  wc  have  learned  respecting  this  wonderful  his- 
tory has  served  strangely  to  change  some  of  our  precon- 
ceived ideas.  We  must  now  be  prepared  to  admit  that 
an  Eden  can  be  planted  even  in  Spitzbergen,  that  there 
are  possibilities  in  this  old  earth  of  ours  which  its  present 
condition  does  not  reveal  to  us  ;  that  the  present  state  of 
the  world  is  by  no  means  the  best  possible  in  relation  to 
climate  and  vegetation  ;  that  there  have  been  and  might 
be  again  conditions  which  could  convert  the  ice-clad  arc- 
tic regions  into  blooming  paradises,  and  which  at  the 
same  time  would  moderate  the  fervent  heat  of  the  tropics. 
We  are  accustomed  to  say  that  nothing  is  impossible  with 
God  ;  but  how  little  have  we  kaown  of  the  gigantic  pos- 
sibilities which  lie  hidden  under  some  of  the  most  com- 
mon of  his  natural  laws  ! 

These  facts  have  naturally  been  made  the  occasion  of 
speculations  as  to  the  spontaneous  development  of  plants 
by  processes  of  varietal  derivation.  It  would,  from  this 
point  of  view,  be  a  nice  question  to  calculate  how  many 
revolutions  of  climate  would  suffice  to  evolve  the  first  land- 
plant  ;  what  are  tlie  chances  that  such  plant  would  be  so 
dealt  with  by  physical  changes  as  to  be  preserved  and 
nursed  into  a  meagre  flora  like  that  of  the  Upper  Silurian 
or  the  Jurassic  ;  how  many  transportations  to  Greenland 
would  suffice  to  promote  such  meagre  flora  into  the  rich 
and  abundant  forests  of  the  Upper  Cretaceous,  and  to 
people  the  earth  with  the  exuberant  vegetation  of  the 
early  Tertiary.  Such  problems  we  may  never  be  able  to 
solve.  Probably  they  admit  of  no  solution,  unless  we  in- 
voke the  action  of  an  Almighty  mind,  operating  through 
long  ages,  and  correlating  with  boundless  power  and  wis- 
dom all  the  energies  inherent  in  inorganic  and  organic 


11 


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258 


THE  GEOLOGICAL   HISTORY  OF  PLANTS. 


nature.  Even  then  we  sliall  perliaps  be  able  to  compre- 
hend only  the  means  by  which,  after  specific  types  have 
been  created,  they  may,  by  the  culture  of  their  Maker, 
be  "sported"  into  new  varieties  or  subspecies,  and  thus 
fitted  to  exi^t  under  different  conditions  or  to  occupy 
higher  places  in  the  economy  of  nature. 
..  Before  venturing  on  such  extreme  speculations  as 
some  now  current  on  questions  of  this  kind,  we  would 
require  to  know  the  successive  extinct  floras  as  perfectly 
as  those  of  the  modern  world,  and  to  be  able  to  ascertain 
to  what  extent  each  species  can  change  either  spontane- 
ously or  under  the  influence  of  struggle  for  existence  or 
expansion  under  favourable  conditions,  and  under  arctic 
semi-annual  days  and  nights,  or  the  shorter  days  of  the 
tropics.  Such  knowledge,  if  ever  acquired,  it  may  take 
ages  of  investigation  to  accumulate. 

As  to  the  origin  and  mode  of  introduction  of  succes- 
sive floras,  I  am,  for  the  reasons  above  stated,  not  disposed 
to  dogmatise,  or  to  adopt  as  final  any  existing  theory  of 
the  development  of  the  vegetable  kingdom.  Still,  some 
laws  regulating  the  progress  of  vegetable  life  may  be 
recognised,  and  I  propose  to  state  these  in  connection 
with  the  Pala3ozoic  floras,  to  which  my  own  studies  have 
chiefly  related. 

Fossil  plants  are  almost  proverbially  uncertain  with 
reference  to  their  accurate  determination,  and  have  been 
regarded  as  of  comparatively  little  utility  in  the  decision 
of  general  questions  of  palaeontology.  This  results  prin- 
cipally from  the  fragmentary  condition  in  which  they 
have  been  studied,  and  from  the  fact  that  fragments  of 
animal  structures  are  more  definite  and  instructive  than 
corresponding  portions  of  plants. 

It  is  to  be  observed,  however,  that  our  knowledge  of 
fossil  plants  becomes  accurate  in  proportion  to  the  extent 
to  which  we  can  carry  the  study  of  specimens  in  the  beds 
in  which  they  are  preserved,  so  as  to  examine  more  per- 


fHMt 


Ifiii  i 


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GENERAL  LAWS   OF  ORIGIN  AND   MIGRATION.       259 


beds 


fect  examples  than  those  usually  to  be  louud  in  museums. 
When  structures  are  taken  into  the  account,  as  well  as 
external  forms,  we  can  also  depend  more  confidently  on 
our  results.  Further,  the  abundance  of  specimens  to  be 
obtained  in  particular  beds  often  goes  far  to  make  up  for 
their  individual  imperfection.  The  writer  of  these  pages 
has  been  enabled  to  avail  himself  very  fully  of  these  advan- 
tages ;  and  on  this  account,  if  on  no  other,  feels  entitled 
to  speak  with  some  authority  on  theoretical  questions. 

It  is  an  additional  encouragement  to  pursue  the  sub- 
ject, that,  when  we  can  obtain  definite  information  as  to 
the  successive  floras  of  any  region,  we  thereby  learn  much 
as  to  climate  and  vicissitudes  in  regard  to  the  extent  of 
land  and  water ;  and  that,  with  reference  to  such  points, 
the  evidence  of  fossil  plants,  when  properly  studied,  is, 
from  the  close  relation  of  plants  to  those  stations  and 
climates,  even  more  valuable  tlian  that  of  animal  fossils. 

It  is  necessary,  however,  that  in  pursuing  such  in- 
quiries we  should  have  some  definite  views  as  to  the 
nature  and  permanence  of  specific  forms,  whether  with 
reference  to  a  single  geological  period  or  to  successive 
periods  ;  and  I  may  be  excused  for  stating  here  some  gen- 
eral principles,  which  I  think  important  for  our  guidance. 

1.  Botanists  proceed  on  the  assumption,  vindicated  by 
experience,  that,  within  the  period  of  human  observation, 
species  have  not  materially  varied  or  passed  into  each 
other.  We  may  make,  for  practical  purposes,  the  same 
assumption  with  regard  to  any  given  geological  period, 
and  may  hold  that  for  each  such  period  there  are  specific 
types  which,  for  the  time  at  least,  are  invariable. 

2.  W^hen  we  inquire  what  constitutes  a  good  species 
for  any  given  period,  we  have  reason  to  believe  that  many 
names  in  our  lists  represent  merely  varietal  forms  or  er- 
roneous determinations.  This  is  the  case  even  in  the 
modern  flora  ;  and  in  fossil  floras,  through  the  poverty  of 
specimens,  their  fragmentary  condition,  and  various  states 


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260 


THE  GEOLOGICAL  HISTORY   OF  PLANTS. 


of  preservation,  it  is  still  more  likely  to  occur.  Every 
revision  of  any  group  of  fossils  detects  numerous  syn- 
onyms, and  of  these  many  are  incapable  of  detection 
without  the  comparison  of  large  suites  of  specimens. 

3.  We  may  select  from  the  flora  of  any  geological  pe- 
riod certain  forms,  which  I  shall  call  specific  types,  which 
may  for  sucii  period  be  regarded  as  unchanging.  Having 
settled  such  types,  we  may  compare  them  with  similar 
forms  in  other  periods,  and  such  comparisons  will  not  be 
vitiated  by  the  uncertainty  which  arises  from  the  com- 
parison of  so-called  species  which  may,  in  many  cases,  be 
mere  varietal  forms,  as  distinguished  from  specific  types. 
Our  types  may  be  founded  on  mere  fragments,  provided 
that  these  are  of  such  a  nature  as  to  prove  that  they  be- 
long to  distinct  forms  which  cannot  pass  into  each  other, 
at  least  within  the  limits  of  one  geological  period. 

4.  When  we  compare  the  specific  tjpes  of  one  period 
with  those  of  another  immediately  precedent  or  subse- 
quent, we  shall  find  that  some  continue  unchanged 
through  long  intervals  of  geological  time,  that  others  are 
represented  by  allied  forms  regarded  either  as  varietal  or 
specific,  and  as  derived  or  otherwise,  according  to  the 
view  which  we  may  entertain  as  to  the  j^ermanence  of 
species.  On  the  other  hand,  we  also  find  new  types  not 
rationally  deducible  on  any  theory  of  derivation  from 
those  known  in  otiier  periods.  Further,  in  comparing 
the  types  of  a  poor  period  with  those  of  one  rich  in  spe- 
cies, we  may  account  for  the  appearance  of  new  types  in 
the  latter  by  the  deficiency  of  information  as  to  the  for- 
mer ;  where  many  new  types  appear  in  the  poorer  period 
this  conclusion  seems  less  probable.  For  example,  new 
types  appearing  in  poor  formations,  like  the  Lower  Erian 
and  Lower  Carboniferous,  have  greater  significance  than  if 
they  appeared  in  the  Middle  Erian  or  in  the  Coal  Measures. 

5.  When  specific  types  disappear  without  any  known 
successors,   under  circumstances  in  which  it  seems  un- 


GENERAL  LAWS  OF  ORIGIN    AND   MIGRATION.       2G1 


likely  that  we  should  have  failed  to  discover  their  con- 
tinuance, we  may  fairly  assume  that  they  have  become 
extinct,  at  least  locally  ;  and  where  the  field  of  observa- 
tion is  very  extensive,  as  in  the  great  coal-fields  of  Europe 
and  America,  we  may  esteem  such  extinction  as  practi- 
cally general,  at  least  for  the  northern  hemisphere. 
When  many  specific  types  become  extinct  together,  or  in 
close  succession,  we  may  suppose  that  such  extinction 
resulted  from  physical  changes  ;  but  where  single  types 
disappear,  under  circumstances  in  which  others  of  similar 
habit  continue,  we  may  not  unreasonably  conjecture  that, 
as  Pictet  has  argued  in  the  case  of  animals,  such  tyi)e8 
may  have  been  in  their  own  nature  limited  in  duration, 
and  may  have  died  out  witliout  any  external  cause. 

6.  With  regard  to  the  introdtiction  of  specific  types 
we  have  not  as  yet  a  sufficient  amount  of  information. 
Even  if  we  freely  admit  that  ordinary  specific  forms,  as 
well  as  mere  varieties,  may  result  from  derivation,  this  by 
no  means  excludes  the  idea  of  primitive  specific  types 
originating  in  some  other  way.  Just  as  the  chemist,  after 
analysing  all  compounds  and  ascertaining  all  allotropic 
forms,  arrives  at  length  at  certain  elements  not  mutually 
transmutable  or  derivable,  so  the  botanist  and  zoologist 
must  expect  sooner  or  later  to  arrive  at  elementary 
specific  types,  which,  if  to  be  accounted  for  at  all,  must 
be  explained  on  some  principle  distinct  from  that  of 
derivation.  The  position  of  many  modern  biologists,  in 
presence  of  this  question,  may  be  logically  the  same  with 
that  of  the  ancient  alchemists  with  reference  to  the 
chemical  elements,  though  the  fallacy  in  tlie  case  of  fos- 
sils may  be  of  more  difficult  detection.  Our  business  at 
present,  in  the  prosecution  of  pala3obotany,  is  to  discover, 
if  possible,  what  are  elementary  or  original  types,  and,  hav- 
ing found  these,  to  enquire  as  to  the  law  of  their  creation. 

7.  In  prosecuting  such  questions  geographical  rela- 
tions must  be  carefully  considered.     When  the  floras  of 

24 


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It 


■   'li  '< 


262 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


two  successive  periods  have  existed  in  the  same  region, 
and  under  circumstances  that  render  it  probable  that 
plants  have  continued  to  grow  on  the  same  or  adjoining 
areas  throughout  these  periods,  the  comparison  becomes 
direct,  and  this  is  the  case  with  the  Erian  and  Carbonifer- 
ous floras  in  northeastern  America.  But,  when  the 
areas  of  the  two  formations  are  widely  separated  in  space 
as  well  as  in  time,  any  resemblances  of  facies  that  we  may 
observe  may  have  no  connection  whatever  with  an  un- 
broken continuity  of  specific  types. 

I  desire,  however,  under  this  head,  to  affirm  my  con- 
viction that,  with  reference  to  the  Erian  and  Carbonifer- 
ous floras  of  North  America  and  of  Europe,  the  doctrine 
of  "homotaxis,"  as  distinct  from  actual  contemporaneity, 
has  no  place.  The  succession  of  formations  in  the  Pala30- 
zoic  period  evidences  a  similar  series  of  physical  phenom- 
ena on  the  grandest  scale  throughout  the  northern  hemi- 
sphere. The  succession  of  marine  animals  implies  the 
continuity  of  the  sea-bottoms  on  which  they  lived.  Tlie 
headquarters  of  the  Erian  flora  in  America  and  Europe 
must  have  been  in  connected  or  adjoining  areas  in  the 
North  Atlantic.  The  similarity  of  the  Carboniferous  flora 
on  the  two  sides  of  the  Atlantic,  and  the  great  number  of 
identical  species,  proves  a  still  closer  connection  in  that 
period.  These  coincidences  are  too  extensive  and  too  fre- 
quently repeated  to  be  the  result  of  any  accident  of  similar 
sequence  at  different  times,  and  this  more  especially  as 
they  extend  to  the  more  minute  differences  in  the  feat- 
ures of  each  period,  as,  for  instance,  the  floras  of  the 
Lower  and  Upper  Devonian,  and  of  the  Lower,  Middle, 
and  Upper  Carboniferous. 

8.  Another  geographical  question  is  that  which  relates 
to  centres  of  dispersion.  In  times  of  slow  subsidence  of 
extensive  areas,  the  plants  inhabiting  such  areas  must  be 
narrowed  in  their  range  and  often  separated  from  one 
another  in  detached  sj)ots,  while,  at  the  same  time,  impor- 


GENERAL   LAWS  OF  ORIGLV   AND   MIGRATION.       2C3 


tant  climatal  clianges  must  also  occur.  On  tlie  rc-cmer- 
gence  of  the  land  such  of  these  species  as  remained  would 
again  extend  themselves  over  their  former  areas  of  distri- 
bution, in  so  far  as  the  new  climatal  and  other  conditions 
would  permit.  We  would  naturally  suppose  that  the  frst 
of  the  above  processes  would  tend  to  the  elimination  of 
varieties,  the  second,  to  their  increase  ;  but,  on  the  other 
hand,  the  breaking  up  of  a  continental  flora  into  that  of 
distinct  islets,  and  the  crowding  together  of  many  forms, 
might  be  a  process  fertile  in  the  production  of  some  varie- 
ties if  fatal  to  others. 

FrHher,  it  is  possible  tiiat  these  changes  of  subsidence 
may  have  some  connection  with  the  introduction,  as  well 
as  with  the  extinction,  even  of  specific  types.  It  is  cer- 
tain, at  least,  in  the  case  of  land-plants,  that  such  types 
come  in  most  plentifully  immediately  after  elevation, 
though  they  are  most  abundantly  preserved  in  periods  of 
slow  subsidence.  I  do  not  mean,  however,  that  this  con- 
nection is  one  of  cause  and  effect ;  there  are,  indeed,  in- 
dications that  it  is  not  so.  One  of  these  is,  that  in  some 
cases  the  enlargement  of  the  area  of  the  land  seems  to  be 
as  injurious  to  terrestrial  species  as  its  diminution. 

9.  Another  point  on  which  I  have  already  insisted,  and 
which  has  been  found  to  apply  to  the  Tertiary  as  well  as 
to  the  Palaeozoic  floras,  is  the  appearance  of  new  types 
within  the  arctic  and  boreal  areas,  and  their  migration 
southward.  Periods  in  which  tiie  existence  of  northern 
land  coincided  with  a  general  warm  temperature  of  the 
northern  hemisphere  seem  to  have  been  those  most  fa- 
vourable to  the  introduction  of  new  forms  of  land-plants. 
Hence,  there  has  been  throughout  geological  time  a  gen- 
eral movement  of  new  floras  from  the  Pala3arctic  and 
Nearctic  regions  to  tlie  southward. 

Applying  the  above  considerations  to  the  Erian  and 
Carboniferous  floras  of  North  America,  we  obtain  some 
data  which  may  guide  us  in  arriving  at  general  conclu- 


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THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


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sions.  The  Erian  flora  is  comparatively  poor,  and  its 
types  are  in  the  main  similar  to  those  of  the  Carbonifer- 
ous. Of  these  types  a  few  only  reappear  in  the  middle 
coal-formation  under  identical  forms  ;  a  great  number  ap- 
pear under  allied  forms  ;  some  altogether  disappear.  The 
Erian  flora  of  New  Brunswick  and  Maine  occurs  side  by 
side  with  the  Carboniferous  of  the  same  region ;  so  does 
the  Erian  of  New  York  and  Pennsylvania  with  the  Car- 
boniferous of  those  States.  Thus  we  have  data  for  the 
comparison  of  successive  floras  in  the  same  region.  In 
the  Canadian  region  we  have,  indeed,  in  direct  sequence, 
the  floras  of  the  Upper  Silurian,  the  Lower,  Middle,  and 
Upper  Erian,  and  the  Lower,  Middle,  and  Upper  Car- 
boniferous, all  more  or  less  distinct  from  each  other,  and 
affording  an  admirable  series  for  comparison  in  a  region 
whose  geographical  features  are  very  broadly  marked. 
All  these  floras  are  composed  in  great  part  of  similar 
types,  and  probably  do  not  indicate  very  dissimilar  general 
physical  conditions,  but  they  are  separated  from  each 
other  by  the  great  subsidences  of  the  Corniferous  lime- 
stone and  the  Lower  Carboniferous  limestone,  and  by  the 
local  but  Intense  subterranean  action  which  has  altered 
and  disturbed-  the  Erian  beds  toward  the  close  of  that 
period.  Still,  these  changes  were  not  universal.  The 
Corniferous  limestone  is  absent  in  Gaspe,  and  probably  in 
New  Brunswick,  where,  consequently,  the  Erian  flora 
could  continue  undisturbed  during  that  long  period. 
The  Carboniferous  limestone  is  absent  from  the  slopes  of 
the  Appalachians  in  Pennsylvania,  where  a  retreat  may 
have  been  afforded  to  the  Upper  Erian  and  Lower  Car- 
boniferous floras.  The  disturbances  at  the  close  of  the 
Erian  were  limited  to  those  eastern  regions  where  the 
great  limestone-producing  subsidences  were  unfelt,  and, 
on  the  other  hand,  are  absent  in  Ohio,  where  the  sub- 
sidences and  marine  conditions  were  almost  at  a  maxi- 
mum. 


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GENERAL  LAWS  OF  ORIGIN  AND  MIGRATION.       2G5 


may 
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Bearing  in  mind  these  peculiarities  of  the  area  in 
question,  we  may  now  group  in  a  tabular  form  the  dis- 
tinct specific  types  recognised  in  the  Erian  system,  indi- 
cating, at  .lie  same  time,  those  which  are  represented  by 
identical  species  in  the  Ca?'boniferous,  those  represented 
by  similar  species  of  the  same  general  type,  and  those  not 
represented  at  all.  For  example,  Calamites  cannwformis 
extends  as  a  species  into  the  Carboniferous  ;  AsteropJiyl- 
lites  latifolia  does  not  so  extend,  but  is  represented  by 
closely  allied  species  of  the  same  type ;  Nematopliyton 
disappears  altogether  before  we  reach  the  Carboniferous. 


Tiible  of  Erian  a 

nd 

Carboniferous  Specific  Types 

Erian  types.     Represented  in 
Carbouiferous— 

■it 

* 
* 

* 

-  P 

* 
* 
* 

* 

* 
* 

* 
* 

# 

Erian  types.    Represented  in 

Carboniltroiis— 

i| 

* 

«?3 

1.  Syriniroxylon  mirabile? 

2.  Nematoxylon 

3.  Nemutopliyton 

4.  Aporoxylon 

27. 
28. 
29. 
30. 
31. 
32. 
33. 
34. 
1 

35. 
36. 
37. 
38. 
39. 

40. 
41. 

42. 

43. 

44. 
|45. 
'46. 

47. 

48. 

49. 

50. 

51. 

Cordaites  Robbii 

C.  angustifolia 

Archapopteris  Jacksoni 

Aneimitcs  obtusa 

Platyphyllum  Erownii . 

Cyclopteris  varia 

C.  obtusa 

* 
* 

6.  Onnoxvlon 

6.  Dadoxylon..  . .    

7.  Sigillaria  Vanuxcmii  . . 

* 

8.  S.  palpebrfi 

Ncuropteris     polymor- 
plia 

9.  Didyniophyllum 

10.  Calamodondron 

* 

N.  scrrulata 

* 

11,  Calamites  transitionis. . 

12.  C  canna>fornii3 

N.  retorquata 

N.  rosecta  

* 

13.  Astcrophyllitcs  scutigc- 
ra              

Megalopteris  Dawsoni. 
Sphcnopteris   Iloening- 

hausi 

S.  llarttii 

14.  A.  latifolia 

15.  Annularia  laxa 

* 

16.  Sphenophyllum       anti- 
quum   

HymcnophyUites  curti- 
lobus 

17.  Cyclostignia 

18.  Arthrostiijma 

19.  Lepidodcndro     Gaspia- 

num 

II.  obtui^ilobus 

Alethopteris  dlscrepans 
Pecopteris  scrrulata. . . 
P.  preciosa 

# 
* 

* 

20.  L.  corrugatum 

''1.  Lycopoditcs  Matthowi  . 

22.  L.  Richardsoni 

23.  Ptilophyton  Vanuxomii 

24.  Lcpidophloios  antiquus. 

25.  Psilophyton  ptiuccps.  . 

26.  P.  robu3tiu9 

Trichomanitcs 

Callipteris 

Cardiocarpum 

C   Crampii 

* 
* 

* 

Antholithcs 

* 

Trigonocarpum 

« 

i-  ■ 


M' 


!'  * 


•!*; 


200 


THE   GEOLOGICAL  HISTORY  OF  PLANTS. 


Of  the  above  forms,  fifty-one  in  all,  found  in  tlie  Erian 
of  eastern  America,  all,  except  the  last  four,  are  certainly 
distinct  specific  types.  Of  these  only  four  reap})ear  in  the 
Carboniferous  under  identical  species,  but  no  less  than 
twenty-six  reappear  under  representative  or  allied  forms, 
some  at  least  of  Avhich  a  derivationist  might  claim  as 
modified  descendants.  On  the  other  hand,  nearly  one 
half  of  the  Devonian  types  are  unknown  in  the  Carbon- 
iferous, while  there  remain  a  very  large  number  of  Car- 
boniferous types  not  accounted  for  by  anything  known  in 
the  Devonian.  Further,  a  very  poor  flora,  including  only 
two  or  three  types,  is  the  predecessor  of  the  Erian  flora  in 
the  Upper  Silurian,  and  the  flora  again  becomes  poor  in 
the  Upper  Devonian  and  Lower  Carbonifer  )us.  Every 
new  species  discovered  must  more  or  less  modify  the  above 
statements,  and  the  whole  Erian  flora  of  America,  as  well 
as  the  Carboniferous,  requires  a  thorough  comparison  with 
tliat  of  Europe  before  general  conclusions  can  be  safely 
drawn.  In  the  mean  time  I  may  indicate  the  direction  in 
wliicli.  the  facts  seem  to  point  by  the  following  general 
statements  : 

1.  Some  of  the  forms  reckoned  as  specific  in  the  De- 
vonian and  Carboniferous  may  be  really  derivative  races. 
There  are  indications  that  such  races  may  have  originated 
in  one  or  more  of  ttie  following  ways  :  (1)  By  a  natural 
tendency  in  synthetic  types  to  become  specialised  in  the 
direction  of  one  or  other  of  their  constituent  elements. 
In  this  way  such  plants  as  Arthrostigma  and  Psilophyton 
may  have  assumed  new  varietal  forms.  (2)  By  embry- 
onic retardation  or  acceleration,*  whereby  certain  species 
may  have  had  their  maturity  advanced  or  postponed,  thus 
giving  them  various  grades  of  perfection  in  reproduction 
and  complexity  of  structure.  The  fact  that  so  many 
Erian  and  Carboniferous  plants  seem  to  be  on  the  con- 


*  In  the  manner  illustrated  hy  Hyatt  and  Cope. 


}on- 


GENERAL   LAWS  OF  ORIGIN  AND  MIGRATION.       267 

fines  of  the  groups  of  Acrogens  and  Gymnosperms  may 
bo  supposed  favourable  to  such  exchanges.  (3)  The  con- 
traction and  breaking  up  of  floras,  as  occurred  in  the 
Middle  Erian  and  Lower  Carboniferous,  may  have  been 
eminently  favourable  to  the  production  of  such  varietal 
forms  as  would  result  from  what  has  been  called  the 
**  struggle  for  existence."  (4)  The  elevation  of  a  great 
expanse  of  new  land  at  the  close  of  the  Middle  Erian  and 
the  beginning  of  the  coal  period  would,  b}'^  permitting 
the  extension  of  species  over  wide  areas  and  fertile  soils, 
and  by  removing  the  pressure  previously  existing,  be 
eminently  favourable  to  the  production  of  new,  and  es- 
pecially of  improved,  varieties. 

2.  Whatever  importance  we  may  attach  to  the  above 
supposed  causes  of  change,  wo  still  require  to  account 
for  the  origin  of  our  specific  types.  This  may  forever 
elude  our  observation,  but  we  may  at  least  hope  to  ascer- 
tain the  external  conditions  favourable  to  their  produc- 
tion. In  order  to  attain  even  to  this  it  will  be  necessary 
to  inquire  critically,  with  reference  to  every  acknowl- 
edged species,  what  its  claims  to  distinctness  are,  so  that 
we  may  be  enabled  to  distinguish  specific  types  from 
mere  varieties.  Having  attained  to  some  certainty  in 
this,  we  may  be  prepared  to  inquire  whether  the  condi- 
tions favourable  to  tlie  appearance  of  new  varieties  were 
also  those  favourable  to  the  creation  of  new  types,  or  the 
reverse — whether  these  conditions  were  those  of  compres- 
sion or  expansion,  or  to  what  extent  the  appearance  of 
new  types  may  be  independent  of  any  external  condi- 
tions, other  than  those  absolutely  necessary  for  their 
existence.  I  am  not  without  hope  that  the  further  study 
of  fossil  plants  may  enable  us  thus  to  approach  to  a  com- 
prehension of  the  laws  of  the  creation,  as  distinguished 
from  those  of  the  continued  existence  of  species. 

3.  In  the  nrcsent  state  of  our  knowledge  we  have  no 
good  ground  either  to  limit  the  number  of  specific  types 


J' 


I! 


I 


1 


'  ill    * 


ii 

{; 


'V 


268 


THE  GEOLOGICAL  HISTORY  OF  PLANTS. 


beyond  what  a  fair  study  of  our  material  may  warrant, 
or  to  infer  that  such  piirjiilive  types  must  necessarily 
have  been  of  low  grade,  or  that  progress  in  varietal  forms 
has  always  been  upward.  The  occurrence  of.  such  an 
advanced  and  specialised  type  as  tliat  of  Dadoxylon 
in  the  Middle  Devonian  should  guard  us  against  these 
errors.  The  creative  process  may  have  been  applicable 
to  the  highest  as  well  as  to  the  lowest  forms,  and  subse- 
quent deviations  must  have  included  degradation  as  well 
as  elevation.  I  can  conceive  nothing  more  unreasonable 
than  the  statement  sometimes  made  that  it  is  illogical  or 
even  absurd  to  suppose  that  highly  organised  beings 
could  have  been  produced  except  by  derivation  from  pre- 
viously existing  organisms.  This  is  begging  the  whole 
question  at  issue,  depriving  science  of  a  noble  department 
of  inquiry  on  which  it  has  as  yet  barely  entered,  and  an- 
ticipating by  unwarranted  assertions  conclusions  which 
may  perhaps  suddenly  dawn  upon  us  through  the  inspira- 
tion of  some  great  intellect,  or  may  for  generations  to 
come  baffle  the  united  exertions  of  all  the  earnest  pro- 
moters of  natural  science.  Our  present  attitude  should 
not  be  that  of  dogmatists,  but  that  of  patient  worknrs 
content  to  labour  for  a  harvest  of  grand  generalisations 
which  may  not  come  till  we  have  passed  away,  but  which, 
if  we  are  earnest  and  true  to  Nature  and  its  Creator,  may 
reward  even  some  of  us. 

Within  the  human  period  great  changes  of  distribu- 
tion of  plants  have  occurred,  chiefly  through  the  agency 
of  man  himself,  and  we  have  had  ample  evidence  that 
plants  are  able  to  establish  themselves  and  prosper  in 
climates  and  conditions  to  which  unaided  they  could  not 
have  transported  themselves,  as,  for  instance,  in  the  case 
of  European  weeds  naturalised  in  Australia  and  New  Zea- 
land. Tliere  is,  however,  no  reason  to  believe  that  any 
specific  change  has  occurred  to  any  plant  within  the  Pleis- 
tocene or  modern  period. 


GENERAL  LAWS  OF  ORIGIN  AND  MIGRATION.       269 


In  a  recent  address,  delivered  to  the  biological  section 
of  the  British  Association,  Mr.  Carruthers  has  discussed 
this  question,  and  has  shown  tiiat  the  earliest  vegetable 
opecimens  described  by  Dr.  8chweinfurth  from  the  Egypt- 
ian tombs  present  no  appearance  of  change.  This  fact 
appears  also  in  the  leaves  and  other  organs  of  plants  pre- 
served in  the  nodules  in  the  Pleistocene  clays  of  the  Ot- 
tawa, and  in  specimens  of  similar  age  found  in  various 
places  in  Britain  and  the  continent  of  Europe.* 

The  diflBculties  attending  the  ordinary  theories  of 
evolution  as  applied  to  plants  have  been  well  set  forth  by 
the  same  able  botanist  in  his  '*  Presidential  Address  to 
the  Geological  Association  in  1877,"  a  paper  which  de- 
serves careful  study.  One  of  his  illustrations  is  that 
ancient  willow,  Sallx  polaris,  referred  to  in  a  previous 
chapter,  which  now  lives  in  the  arctic  regions,  and  is 
found  fossil  in  the  Pleistocene  beds  at  Cromer  and  at 
Bovey  Tracey. 

He  notes  the  fact  that  the  genus  Salix  is  a  very  varia- 
ble one,  including  19  subgcneric  groups  and  IGO  species, 
with  no  less  than  2^3  varieties  and  70  hybrids.  Salix 
polaris  belongs  to  a  subgeneric  group  containing  29 
species,  which  are  arranged  in  four  sections,  that  to 
which  S.  polaris  belongs  containing  six  species.  Now  it 
IS  easy  to  construct  a  theoretical  phylogeny  of  the  deri- 
vation of  the  willows  from  a  supposed  ancestral  source, 
but  wlien  we  take  our  little  S.  polaris  we  find  that  this 
one  twig  of  our  ancestral  tree  takes  us  back  withont 
change  to  the  Glacial  period.  The  six  species  would  take 
us  still  farther,  and  the  sections,  subgenera,  and  genus 
at  the  same  rate  would  require  an  incalculable  amount  of 


11  : 


past  time, 
terms  ■ 


lie  concludes  the  inquiry  in 


the  following 


*" Proceedings  British  Astiociation,"  1886,   "Pleistocene  Plants  of 
Canada,"  Canadian  Naturalist,  1866. 


\i 


m 


■  ii;; 


ill! 


270 


THE  GEOLOGICAL  UISTORY  OF  PLANTS. 


"But  when  we  have  reached  the  branch  representing 
the  generic  form  we  have  made  but  little  progress  in  the 
phylogenesis  of  Salix.  With  Populus  this  genus  forms 
a  small  order,  Salicineae.  The  two  genera  are  closely 
allied,  yet  separated  by  well-marked  characters ;  it  is 
not,  however,  difficult  to  conceive  of  both  having  sprung 
from  a  generalised  form.  But  there  is  no  record  of  such 
a  form.  The  two  genera  appear  together  among  the 
earliest  known  dicotyledons,  the  willows  being  repre- 
sented by  six  and  the  poplars  by  nine  species.  The  or- 
dinal form,  if  it  ever  existed,  must  necessarily  be  much 
older  than  the  period  of  the  Upper  Cretaceous  rocks, 
that  is,  than  the  period  to  which  the  earliest  known 
dicotyledons  belong. 

*'  The  Salicineae  are  related  to  five  other  natural 
orders,  in  all  of  which  the  apetalous  flowers  are  arranged 
in  catkins.  These  different  though  allied  orders  must 
be  led  up  by  small  modifications  to  a  generalised  amcn- 
tiferous  type,  and  thereafter  the  various  groups  of  apetal- 
ous plants  by  innumerable  eliminations  of  differentiating 
characters  until  the  primitive  form  of  the  apetalous  plant 
is  reached.  Beyond  this  the  uncurbed  imagination  Avill 
have  more  active  work  in  bridging  over  the  gap  between 
Angiosperms  and  Gymnospcrms,  in  finding  the  interme- 
diate forms  that  led  up  to  the  vascular  cryptogams,  and 
on  through  the  cellular  plants  to  the  priix^ordial  germ. 
Every  step  in  this  phylogeiietic  tree  must  be  imagined. 
The  earliest  dicotyledon  takes  us  not  a  step  farther  back 
in  the  phylogenetic  history  of  Salix  than  that  supplied 
by  existing  vegetation.  All  beyond  the  testimony  of  our 
living  willows  is  pure  imagination,  unsupported  by  a 
single  fact.  So  that  here,  also,  the  evidence  is  against 
evolution,  and  there  is  none  in  favour  of  it." 

It  is  easy  to  see  that  similar  difficulties  beset  every 
attempt  to  trace  the  development  of  plants  on  the  prin- 
ciple of  slow  and  gradual  evolution,  and  we  are  driven 


GENEUAl   LAWS  OF  ORIGIN  AND   MIGRATION.       271 


back  on  the  theory  of  periods  of  rapid  origin,  as  we  liave 
already  seen  suggested  by  Saporta  in  the  case  of  the  '"'re- 
taceous  dicotyledons.  Such  abrupt  and  plentiful  intro- 
duction of  species  over  large  areas  at  the  same  time,  by 
whatever  cause  effected — and  we  are  at  present  quite  igno- 
rant of  any  secondary  causes — becomes  in  effect  something 
not  unlike  the  old  and  familiar  idea  of  creation.  Science 
must  indeed  always  be  balfled  by  questions  of  ultimate 
origin,  and,  however  far  it  may  be  able  to  trace  the  chain 
of  secondary  causation  and  development,  must  at  length 
find  itself  in  the  presence  of  the  great  Creative  Mind, 
who  is  **  before  all  things  and  in  whom  all  things  con- 
sist." 


APPENDIX. 


I.— COMPARATIVE  VIEW  OF  THE  SUCCESSIVE  FALMO- 
ZOIC  FLORAS  OF  NORTHEASTERN  AMERICA  AND 
GREAT  BRITAIN. 

In  eastern  Canada  there  is  a  very  complete  series  of  fossil  j)lants, 
extending  from  the  Silurian  to  the  Permian,  and  intermediate  in  its 
species  between  the  floras  of  interior  America  and  of  Europe.  I  may 
use  this  succession,  mainly  worked  out  by  myself,*  to  summarise  the 
various  PaK-Pozoic  floras  and  sub-floras,  in  order  to  give  a  condensed 
view  of  this  portion  of  the  history  of  the  vegetable  kingdom,  and  to 
direct  attention  to  the  important  fact,  too  often  overlooked,  that 
there  is  a  definite  succession  of  fossil  plants  as  well  as  of  animals, 
and  that  this  is  important  as  a  means  of  determining  geological 
horizons.  A  British  list  for  comparison  has  been  kindly  prepared 
for  me  by  Mr,  R.  Kidston,  F.  G.  S.  For  lists  referring  to  the  west- 
em  and  southern  portions  of  America,  I  may  refer  to  the  reports  of 
Lesquereux  and  Fontaine  and  White.f 

In  this  connection  I  am  reminded,  by  an  excellent  little  paper  of 
M.  Zoiller,  f  on  Carboniferous  plants  from  the  region  of  the  Zambesi, 
in  Africa,  that  the  flora  which  in  the  Carboniferous  period  extended 
over  the  temperate  portions  of  the  northern  hemisphere  and  far  into 
the  arctic,  also  passed  across  the  equator  and  prevailed  in  the  south- 
ern hemisphere.  Of  eleven  species  brought  from  the  Zambesi  by  M. 
Lapierre  and  examined  by  M.  Zeiller,  all  were  identical  with  Euro- 

*  "  Acadian  Oeology,"  "  Reports  on  Fossil  Plants  of  Canada,"  Geo- 
logical Survey  of  Canada. 

\  "Geological  Surveys  of  Pennsylvania,  Ohio,  and  Illinois.'* 
i  Paris,  1883. 
20 


I 


i' 


'f 


274 


APPENDIX. 


pean  species  of  the  upper  coal-formation,  an  the  same  fact  has  been 
observed  in  the  coal  flora  of  the  Cape  Colony.*  These  facts  bear 
testimony  to  the  remarkable  uniformity  of  climate  and  vegetation  in 
the  coal  period,  and  I  perfectly  agree  with  Zeiller  that  'hey  show, 
when  taken  in  connection  with  other  parallelisms  in  fossils,  an  actual 
contemporaneousness  of  the  coal  llora  over  the  whole  world. 


m 


1.  Carboniferous  Flora. 
(1)  Permo-Carboiiiferotis  Sub-Flora :  ''^- 

This  occurs  in  the  upper  member  of  the  Carboniferous  system  of 
Nova  Scotia  and  Prince  Edward  Island,  originally  named  by  the 
writer  the  Newer  Coal-formation,  and  more  recently  the  Permo- 
Caiboniferous,  and  the  upper  beds  of  which  may  not  improbably  be 
contemporaneous  with  the  Lower  Permian  or  Lower  Dyas  of  Europe. 
In  this  formation  there  is  a  predominance  of  red  sandstones  and 
shales,  and  i^  contains  no  productive  beds  of  coal.  J  ;  fossil  plants 
are  for  the  moot  part  of  species  found  in  the  Middle  r  Productive 
Coal-formation,  but  arc  less  numerous,  and  there  are  a  few  new  forms 
akin  to  those  of  the  European  Permian.  The  most  characteristic 
species  of  the  upper  portion  of  the  formation,  which  has  the  most 
decidedly  Permian  aspect,  are  the  following: 

Dadoxylon  materiarium,  Dawson. 

Walchia  {Araiicarites)  robusta,  Dn.  ;  v;  m   ''.        ••  "-. 

W.  {A.)  gracilis,  T>ii.   ,    ,.t  j.  ■  '  j 

*  W.  imbricatula.  On.  .;  ■  .'.  •  ;  .• ; 
Calamites  SHckovii,TiTonQ\>,  '  ,  '|'*' /  .::...•.  I 
C:  (7i«/i/,  Brongt.                    ■:      :     ■        r  I  ,'';       '-      .     -> 

*  C.  gigas,'Qvongi.  '■•'    ■       ;  .  r 
Neuropteris  rarinervis,  Bunbury.          ■           '      :.        ....      ,u 

^  -       Alethopleris  nervosa,  Brongt.  •.     .  !^ 

Pecopieris  arborescens,  Brongt.     .      ^  ,     '  ■     ,    .  ! 

*  P.  rigida,  Bn.  .  ...,.'  '  ' 
P.  oreopteroides,  Brongt.     -.      ,.    .i           ;    -.          ■..  r  •;  ' :,  *  .•_■  ? 

*  Cordaites  simplex,  Dn. 

Of  these  species,  those  marked  with  an  asterisk  have  not  yet  been 
found  in  the  middle  or  lower  members  of  the  Carboniferous  system. 
They  will  be  found  described,  and  several  of  them  figured,  in  my 
'*  Report  on  the  Geology  of  Prince  Edward  Island.''  f  The  others  are 

*  Grey,  "  Journal  of  the  Geological  Society,"  vol.  xxvii. 
t  1871. 


' 


APPENDIX. 


275 


common  and  widely  diffused  Carl)oniforous  species,  some  of  which 
have  extended  to  the  Permian  period  in  Knrope  as  well.  From  tho 
upper  beds,  characterised  by  these  and  a  few  other  s{)ccies,  there  is  a 
gradual  passage  downward  into  the  productive  coal-measures,  and  a 
gradually  increasing  number  of  true  coal-formation  species. 

It  is  worthy  of  remark  here  that  the  association  in  the  Permo- 
Carboniferous  of  numerous  trunks  of  Dadoxijlon  with  the  branches 
of  Walchia  and  with  fruits  of  tho  character  of  Triyonocarpa,  seems 
to  show  that  these  were  parts  of  one  and  the  same  plant. 

This  formation  represents  the  Upper  IJarren  Measures  of  West 
Virj^inia,  which  are  well  described  by  Fontaine  and  White,*  and  the 
reasons  which  these  authors  ailduce  for  considering  the  latter  equiv- 
alent to  the  European  Permian  will  apply  to  tho  more  northern  and 
eastern  deposits  as  well,  though  these  have  afforded  fewer  s|)ecies  of 
plants,  and  are  ai)parently  less  fully  developed. 

(2)  Coal-formation  Sub-Flora : 

The  Middle  or  Productive  Coal-formation,  containing  all  the  beds 
of  coal  which  are  mined  in  Nova  Scotia  and  '.'ape  Broton,  is  the  head- 
quarters of  the  C'arlxiniferous  flora.  From  this  formation  I  have 
catalogued  f  one  hundred  and  thirty-five  species  of  plants ;  but,  as 
several  of  these  are  founded  on  imperfect  specimens,  the  number  of 
actual  species  may  be  estimated  at  one  hundred  and  twenty.  Of 
these  more  than  one  half  are  species  common  to  Euro[X!  and  America. 
No  less  than  nineteen  species  are  SigiUaria',  and  about  the  sjimo 
number  are  Lepidodcndra.  About  fifty  are  ferns  and  thirteen  are 
Calamites,  Asterophyllites,  and  Sphenophylla.  The  great  abundance 
and  number  of  sper-  s  of  JSigillariw,  Lepidodcndra,  and  ferns  are 
characteristic  of  this  sub-flora ;  and  among  the  ferns  certain  species 
of  Neuropteris,  Pecopteris,  Alethopteris,  and  Sphenopteria  greatly 
preponderate. 

These  beds  are  the  equivalents  of  the  Middle  Coal-measures,  or 
Productive  Coal-measures  of  Pennsylvania,  Ohio,  &c,,  and  of  the 
coal-formation  proper  of  various  European  countries.  Very  many 
of  the  species  are  common  to  Nova  Scotia  and  Pennsylvania;  but  in 
proceeding  westward  the  number  of  identical  siHJcies  seems  to  di- 
minish. 


"  Report  on  the  Permian  Flora  of  Western  Virginia  and  South 
Pennsylvania,"  1880.  .... 

f  '•  Acadian  Geology,"  and  "  Keport  on  Flora  of  Lower  Carhonifer- 
ous,"  1873. 


if; 


M  ft      i 


mi 


Pi 


276 


APPENDIX. 


(3)  The  Millstone  Grit  Sub-Flora : 

In  this  formation  the  abundanoc  of  jilants  and  the  number  of 
species  are  greatly  diminished.*  Trunks  of  coniferous  trees  of  the 
species  Dadoxylon  Acadianum,  having  wide  wood-cells  with  three 
or  more  series  of  discs  and  complex  medullary  rays,  become  charac- 
teristic. Calamites  tmdulatum  is  abundant  and  seems  to  replace  C. 
Suckovii,  though  C.  cannceformis  and  C.  cistii  continue.  JSigillarim 
become  very  rare,  and  the  species  of  Lepidodendron  are  few,  and 
mostly  those  with  large  leaf-bases.  Lepidophloios  still  continues,  and 
Cordaites  abounds  in  some  beds.  The  ferns  are  greatly  reduced, 
though  a  few  characteristic  coal-formation  species  occur,  and  the 
genus  Cardiopteris  appears.  Beds  of  coal  are  rare  in  this  formation ; 
but  where  they  occur  there  is  in  connection  with  them  a  remarkable 
anticipation  of  the  rich  coal-formation  flora,  which  would  thus  seem 
to  have  existed  locally  in  the  Millstone  Grit  period,  but  to  have 
found  itself  limited  by  generally  unfavorable  conditions.  In  Ameri- 
ca, as  in  Europe,  it  is  in  the  north  that  this  earlier  development  of 
the  coal-flora  occurs,  while  in  the  south  there  is  a  lingering  of  old 
forms  in  the  newer  bods.  In  Newfoundland  and  Cape  Breton,  for 
instance,  as  well  as  in  Scotland,  productive  coal-beds  and  a  greater 
variety  of  species  of  plants  occur  in  this  formation. 

The  following  would  appear  to  be  the  equivalents  of  this  forma- 
tion, in  flora  and  geological  position  : 

1.  The  Serai  Conglomerate  of  Rogers  in  Pennsylvania,  &c. 

2.  The  Lower  Coal-formation  Conglomerate  and  Chester  groups 
of  Illinois  (Worthen). 

3.  The  Lower  Carboniferous  Sandstone  of  Kentucky,  Alabama, 
and  Virginia. 

4.  The  Millstone  Grit  and  Yoredale  rocks  of  northern  England, 
and  the  Culmiforous  of  Devonshire. 

5.  The  Moor  rock  and  Lower  Coal-measures  of  Scotland. 

6.  Flagstones  and  Lower  Shales  of  the  south  of  Ireland,  and  Mill- 
stone Grit  of  the  north  of  Ireland. 

7.  The  JQngste  Grauwucke  of  the  Ilartz,  Saxony,  and  Silesia. 

(4)  The  Carhnniferons  Limestone  Series : 

This  affords  few  fossil  plants  in  eastern  America,  and  in  so  far  as 
known  they  are  similar  to  those  of  the  next  group.  In  Scotland  it 
is  richer  in  plants,  but,  according  to  Mr.  Kidston,  these  are  largely 

*  "  Report  on  J'ossJl  Plants  of  the  Lower  Carboniferous  and  Millstone 
Grit  of  Canada,"  1813. 


APPENDIX. 


277 


similar  to  those  of  the  underlying  beds,  though  with  some  species 
which  extend  upward  into  the  Millstone  Grit.  In  Scotland  the  alga 
named  Spirophyton  and  Arch(tocalamites  radiatus — which  in  Amer- 
ica are  Erian — appear  in  this  formation. 


Mill- 


Istone 


(5)  TJie  Lower  Carboniferous  Sub-Flora :  -^ 

This  group  of  plants  is  best  seen  in  the  shales  of  the  Horton 
series,  under  the  Lower  Carboniferous  marine  limestones.  It  is 
small  and  peculiar.  The  most  characteristic  species  are  the  follow- 
ing: 

Dadoxylon  {Palmoxylon)  antiquius,  Dn. — A  species  with  large 
medullary  rays  of  three  or  more  series  of  cells. 

Lepidodendron  corrugatum,  Dn. — A  species  closely  allied  to  L. 
VeWieimianum  of  Europe,  and  which  is  its  American  representative. 
This  is  perhaps  the  most  characteristic  plant  of  the  formation.  It 
is  very  abundant,  and  presents  very  protean  appearances,  in  its  old 
stems,  branches,  twigs,  and  Knorria  forms.  It  had  well-character- 
ised stigmaria  roots,  and  constitutes  the  oldest  erect  forest  known  in 
Nova  Scotia.  ^.      i    .,    -    -  '         ■       . 

Lepidodenaron  ietragonum,  Sternberg.  .. 

L.  obovatum,  Sternb.  -.:.,,,.   -• 

L.  acideatum,Stcrnh.  '.     ,     ,     ,>    \  ,_  ~     .-.    .: 

L.  dichofomuni,  Sternb.  ,>  ^,   ,...     >  ■  .  . ,v    

The  four  species  last  mentioned  are  comparatively  rare,  and  the 
specimens  are  usually  too  imperfect  to  render  their  identification 
certain,  but  Lepidodeudra  are  especially  characteristic  trees  of  this 
horizon. 

Cyclopferis  (Afieimites)  Acadica,  Dn. — A  very  characteristic  fern, 
allied  in  the  form  of  its  fronds  to  C  tenuifoha  of  Goeppcrt,  to  C. 
nana  of  Eichwald,  and  to  Adiantites  antiqnus  of  Stur.  Its  fnictifl- 
cation,  however,  is  nearer  to  that  of  Aneimia  than  to  that  of  Adi- 
antum. 

Ferns  of  the  genera  Cardiopteris  and  Ilymenophyllites  also  occur, 
though  rarely. 

Ptilophyton  plumula,  Dn. — This  is  the  latest  appearance  of  this 
Erian  genus,  which  also  occurs  in  the  Lower  Carbonilerous  of  Eu- 
rope and  of  the  United  States. 

Cordaiies  borassifolia,  lirongt. 
'    On  the  whole,  this  small  flora  is  markedly  distinct  from  that  of 
the  ^Vlillstone  Grit  and  true  coal-formation,  from  which  it  is  sepa- 
rated by  the  great  length  of  tiuio  require<^or  the  deposition  of  the 
marine  limestones  and  their  associated  beds,  in  which  no  land-plants 


278 


APPENDIX. 


have  been  found  ;  nor  is  this  gap  filled  up  by  the  conglomerates  and 
coarse  arenaceous  beds  which,  as  I  have  explained  in  "  Acadian  Ge- 
ology," in  some  localities  take  the  place  of  the  limestones,  as  they  do 
also  in  the  Aj)palachian  region  farther  south. 

The  palipobotanical  and  strategraphical  equivalents  of  this  scries 
abroad  would  seem  to  be  the  following : 

1.  The  Vespertine  group  of  Rogers  in  Pennsylvania. 

2.  The  Kinderhook  group  of  Worthen  in  Illinois. 

3.  The  Marshall  group  of  Winchell  in  Michigan. 

4.  The  Waverley  sandstone  (in  part)  of  Ohio. 

5.  The  Lower  or  False  Coal-measures  of  Virginia. 

6.  The  Calciferous  sandstones  of  McLaren,  or  Tweedian  group  of 
Tate  in  Scotland. 

7.  The  Lower  Carboniferous  slate  and  Coomhala  grits  of  Jukes 
in  Ireland. 

8.  The  Culm  and  Culm  Grauwacke  of  Germany. 

9.  The  Graywacke  or  Lower  Coal-measures  of  the  Vosges,  as  de- 
scribed by  Schimper. 

10.  The  Older  Coal-formation  of  the  Ural,  as  described  by  Eich- 
wald. 

11.  The  so-called  "  Ursa  Stage  "of  Heer  includes  this,  but  he  has 
united  it  with  Devonian  beds,  so  that  the  name  cannot  be  used  ex- 
cept for  the  local  development  of  these  beds  at  Bear  Island,  Spitz- 
bergcn.  The  Carboniferous  plants  of  arctic  America,  IMelville  Isl- 
and, &c.,  as  well  as  those  of  Spitzbergen,  appear  all  to  be  Lower 
Carboniferous.* 

All  of  the  above  groups  of  rocks  are  characterised  by  the  preva- 
lence of  Lepidodendra  of  the  type  of  L.  corrugaium,  L,  Veltheimia- 
ntim,  and  L.  Olincanum ;  pines  of  the  sub-genus  Pitus  of  VVitham, 
Palccoxylon  of  Brongniart,  and  peculiar  ferns  of  the  genera  Cy- 
cloptcris,  Cardiopteris,  Triphyllopleris,  and  Sphenopteris.  In  all  the 
regions  above  referred  to  they  form  the  natural  base  of  the  great 
Carboniferous  system. 

In  Virginia,  according  to  Fontaine  and  White,  types,  such  as 
Archceopterts,  which  in  the  north  are  Upper  Erian,  occur  in  this 
group.  Unleso  there  have  been  some  errors  in  fixing  the  lower  limit 
of  the  Vespertine,  this  would  indicate  a  longer  continuance  of  old 
forms  in  the  south. 


*  "  Notes  on  Geological  Map  of  the  Northern  Portion  of  the  Dominion 
of  Canada,"  by  Dr.  G.  M.  Dawson,  1887. 


APPENDIX. 


279 


as 
lis 
lit 
Id 


2.  Erian  Flora. 

(1)  Upper  Erian  Suh-Flora : 

This  corresponds  to  the  Catskill  and  Chemung  of  the  New  York 
series,  and  to  the  Upper  Devonian  of  Europe. 

The  flora  of  this  formation,  which  consists  mostly  of  sandstones, 
is  not  rich.  Its  most  distinctive  species  on  both  sides  of  the  Atlantic 
seem  to  be  the  ferns  of  the  genus  Archcpopteris,  along  with  species 
referred  to  the  genus  Cyclopteris,  but  which,  in  so  far  as  their  barren 
fronds  arc  concerned,  for  the  most  part  resemble  Archceopferis. 

The  characteristic  American  species  are  Archceopteris  Jacksoni, 
A.  Rogersi,  and  A.  Gaspiensis.  VycJopteris  obtusa  and  C.  (Platy- 
phyllum)  Brou  lii  are  also  very  characteristic  species.  In  Europe, 
Archceopteris  Hibernica  is  a  prevalent  species. 

Leptophleum  rhombicum  and  fragments  of  Psilophyton  are  also 
found  in  the  Upper  Erian.  There  is  evidence  of  the  existence  of 
vast  numbers  of  Rhizocarps  in  this  period,  in  the  deposits  of  spore- 
cases  (Sporangites  Iluronensis)  in  the  shales  of  Kettle  Point,  Lake 
Huron ;  and  in  deposits  of  similar  character  in  Ohio  and  elsewhere 
in  the  West. 

The  Upper  Erian  flora  is  thus  very  distinct  from  that  of  the 
Lower  Carboniferous,  and  the  unconformable  relation  of  the  beds  in 
the  Northeast  may  perhaps  indicate  a  considerable  lapse  of  time. 
Still,  even  in  localities  where  there  appeal's  to  be  a  transition  from 
the  Carboniferous  into  the  Devonian,  as  in  the  Western  States  and 
in  Ireland,  the  characteristic  flora  of  each  formation  may  be  distin- 
guished, though,  as  already  stated,  there  is  apparently  some  mixture 
in  the  South. 

(2)  Middle  Erian  Sub-Flora  : 

Both  in  Canada  and  the  United  States  that  part  of  the  great 
Erian  system  wiiich  may  be  regarded  as  its  middle  division,  the 
Hamilton  and  Marcellus  shales  of  New  York,  the  Cordaites  shales  of 
St.  John,  New  Brunswick,  and  the  middle  shales  and  sandstones  of 
the  Gaspe  series,  presents  conditions  more  favourable  to  the  abundant 
growth  of  land-plants  than  either  the  upper  or  lower  member.  In 
the  St.  John  beds,  in  particular,  there  is  a  rich  fern  flora,  comparable 
with  that  of  the  coal-formation,  and  numerous  stipe3  of  ferns  and 
trunks  of  tree-ferns  have  been  found  in  the  Hamilton  and  Cornifer- 
ous  series  in  the  West,  as  well  as  trunks  of  Dadorylon,  It  is,  how- 
ever, distinguished  by  a  prevalence  of  small  and  delicate  species,  and 
by  such  forms  as  HymenophyUites  and  the  smaller  Sphenopterids» 
and  also  by  some  peculiar  ferns,  as  Archo'opteris  and  Megalopteria. 


-.iV 


oil-  , 


i 


280 


APPENDIX. 


In  addition  to  ferns,  it  has  small  Lepidodendra,  of  which  L.  Gaspi- 
anum  is  the  chief.  Calamitecn  occur,  ArchcEocalamites  radiatus  being 
the  dominant  species.  This  plant,  which  in  Europe  appears  to  reach 
up  into  the  Lower  Carboniferous,  is  so  far  strictly  Erian  in  north- 
'jiist  America.  Sigillarim  scarcely  appear,  but  Cordaitea  is  abun- 
dant, and  the  earliest  known  species  of  Dadoxylon  appear,  Avhile  the 
Psilophyl.on,  so  characteristic  of  the  Lower  Erian,  still  continues, 
and  the  remfirkaulc  aquatic  plants  of  the  genus  Ptilophyto7i  are 
locally  abundant. 

(3)  Lower  Erian  Sub-Flora : 

Tliis  belongs  to  the  Lower  Devonian  sandstones  and  shales,  and 
is  best  seen  in  that  formation  at  Gaspe  and  the  Bay  des  Chaleurs.  It 
is  equivalent  to  the  Oriskany  sandstone,  so  fai  as  its  animal  fossils 
and  mineral  character  are  concerned.  It  is  characterised  by  the  ab- 
sence of  true  ferns.  Catamites  and  Siyillaria;,  and  by  the  presence 
of  such  forms  as  Psilophyton,  Arthrostiyma,  Leptophleum,  and  iVe- 
matophyton.  Lepidodendron  Gaspiamim  and  Leptophleum  already 
occur,  though  not  nearly  so  abundant  as  Psilophyton. 

The  Lower  Erian  plants  have  an  antique  and  generalised  aspect 
which  would  lead  us  to  infer  that  they  are  near  the  beginning  of  the 
land-flora,  or  perhaps  in  part  belong  to  the  close  of  an  earlier  flora 
still  in  great  part  unknown  •  and  few  indications  of  land-plants  have 
been  found  earlier. 

At  Campbellton  and  Scaumenac  Bay.  on  the  Bay  des  Chaleurs, 
fossil  fishes  of  genera  characteristic  of  the  Lower  ana  Upper  De- 
vonian horizons  respectively,  occur  in  association  with  fossil  plants 
of  these  horizons,  and  have  been  described  by  Mr.  Whiteaves.* 

It  is  interesting  to  note  that,  as  Fontaine  and  White  have  ob- 
served, certain  forms  which  are  Plrian  in  the  northeast  are  found  in 
the  Lower  members  of  the  Carboniferous  in  West  Virginia,  indicat- 
ing the  southward  march  of  species  in  these  periods. 

..  -.. '  -  ■■>  -.>•.:   .■r-i'  :■,:  :.,  ,-   ,.  :,  ■■  ■  ,,     -A    -  '^ 

3.  The  Silurian  Flora  and  still  Earlier  Indications  op 

Plants. 

In  the  upper  beds  of  the  Silurian,  those  of  the  Ilelderberg  series, 
v;e  still  find  Psilophyton  and  JVemafophyfon ;  but  below  these  we 
know  no  land-plants  in  Canada.  In  the  United  States,  Lesquereux 
and  Claypole  have  described  remains  which  may  indicate  the  exist- 
ence of  lyeopodiaeeous  and  annulnrian  types  as  far  back  as  the  be- 


*  a 


Traasactions  of  the  Royal  Society  of  Canada." 


APPENDIX. 


281 


ginning  of  the  Upper  Silurian,  or  even  as  low  as  the  Hudson  River 
group,  and  Hicks  has  found  Ncmatophyton  and  Psilophyton  in  beds 
about  as  old  in  Wales,  along  with  the  uncertain  stems  named  Ber- 
tvi/ni'a.  In  the  Lower  Silurian  the  Protanmilaria  of  the  Skiddaw 
series  in  England  may  represent  a  land-plant,  but  this  is  uncertain, 
and  no  similar  species  has  been  found  in  Canada. 

The  Cambrian  roc'is  are  so  far  barren  of  land-plants;  the  so- 
called  Eo})hyti)ii  being  evidently  nothing  but  markings,  probao.  <^ 
producec^  by  crustaceans  and  other  aquatic  animals.  In  the  still 
older  Laurentian  the  abundant  beds  of  graphite  probably  indicate 
the  existence  of  plants,  but  whether  aquatic  or  terrestrial  it  is  impos- 
sible to  decide  at  present. 

It  would  thus  appear  that  our  certain  knowledge  of  land-vegeta- 
tion begins  with  the  Upper  Silurian  or  Cc  bilurio-Cambrian,  and 
that  its  earliest  forms  were  Acrogens  allied  to  Lycopods,  and  proto- 
typal trees,  forerunnei-s  of  the  Acrogens  or  the  gymnosperms.  In 
the  Lower  Devonian  little  advance  is  made.  In  the  Middle  Devonian 
this  meagre  flora  had  been  replaced  by  one  rivalling  that  of  the  Car- 
boniferous, and  including  pines,  tree-ferns,  and  arboreal  forms  of 
Lycopods  and  of  equisetaeeous  plants,  as  well  as  numerous  herba- 
ceous plants.  At  the  close  of  the  Erian  the  flora  again  became 
meagre,  and  continued  so  in  the  Lower  Carboniferous.  It  again  be- 
came rich  and  varied  in  the  Middle  Carboniferous,  to  decay  in  the 
succeeding  Permian. 


IMOS, 

we 


II.— HEER'S  LATEST  KESULTS  IN  THE  GREENLAND 

FLORA. 

A  VERY  valuable  report  of  Prof.  Steenstrup,  published  in  Copen- 
hagen in  1883,  the  year  in  which  Heer  died,  contains  the  results  of 
his  last  work  on  the  Greenland  plants,  and  is  so  important  that  a 
summary  of  its  contents  will  be  interesting  to  all  students  of  fossil 
botany  or  of  the  vicissitudes  of  climate  which  the  earth  u^^  under- 
gone.* 

The  plant-bearing  beds  of  Greenland  are  as  follows,  in  ascending 
order : 

1.  Cretaceous. 

1.  The  Kome  series,  of  black  shales  resting  on  the  Laurentian 
gneiss.     These  beds  are  found  at  various  other  localities,  but  the 

*  Meddelelser  om  Gronland,  Hefte  V.,  Copenhagen,  1883. 


J 


ili.il 


! 

in.    .. 


f 


iS 


\\    V 


-  •  i 


1 : 

lii 

Si; 

if  i 

h 


u 


II 


282 


APPENDIX. 


name  above  given  is  that  by  which  thoy  are  generally  known.  Their 
flora  is  limited  to  ferns,  cycads.  conifers,  and  a  few  endogens,  with 
only  Populu.H  primcpva  to  represent  the  dicotyledons.  These  beds 
are  regarded  us  Lower  Cretivceous  (Urgonian),  but  the  animal  fossils 
would  seem  to  give  thorn  a  rather  higher  pos.don.  They  may  be 
regarded  as  equivalent  to  the  Kootanie  and  Queen  Charlotte  beds  in 
Canada,  and  the  Potomac  series  in  Virginia. 

2.  The  A  feme  series.  These  also  are  black  shales  with  dark- 
coloured  sandstones.  They  are  best  exposed  at  Upernavik  and 
Waigat.  Here  dicotyledonous  leaves  abound,  amounting  to  ninety 
species,  or  more  than  half  the  whole  number  of  species  found. 
The  fossil  plants  resemble  those  of  the  Dakota  series  of  the  United 
States  and  the  Dunvegan  series  of  Canada,  and  the  animal  fossils 
indi(!ate  the  horizon  of  the  Fort  Pierre  or  its  lower  part.  They  may 
be  regarded  as  representing  the  lower  part  of  the  Upper  Cretaceous. 
The  genera  Fopuliis,  Myrica,  Quercus,  Ficus,  Platanus,  Sassafras, 
Laurus,  3Iac/nolia,  and  Liriodendron  are  among  those  represented 
in  these  beds,  and  the  peculiar  genera  Macclintockia  and  Credneria 
are  characteristic.  The  genus  Pinus  is  represented  by  five  species, 
Sequoia  by  five,  and  Salisburia  by  two,  with  three  of  the  allied 
genus  Baicra.     There  ai'e  many  ferns  and  cycads. 

3.  The  Patoot  series.  These  are  yellow  and  red  shales,  which 
seem  to  owe  their  colour  to  the  spontaneous  combustion  of  pyritous 
lignite,  in  the  manner  observed  on  the  South  Saskatchewan  and  the 
Mackenzie  rivers.  Their  age  is  probably  about  that  of  the  Fox-IIill 
group  or  Senonian,  and  the  Upper  Cretaceous  of  Vancouver  Island, 
and  they  afford  a  large  proportion  of  dicotyledonous  leaves.  The 
genera  of  dicotyledons  are  not  dissimilar  from  those  of  Atane,  but 
we  now  recognise  Pdula  and  Alnus,  Comptonia,  Planera.  Sapo- 
facifes,  Fraxinns,  Viburnutn,  Comus,  Acer,  Celastrus,  Paliurus, 
Ceanothus,  Zizyphus,  and  Cratcpgus  as  new  genera  of  modern  aspect. 

On  the  whole  there  have  been  found  in  all  these  beds  335  species, 
belonging  to  00  families,  of  which  30  are  dicotyledonous,  and  repre- 
sent all  the  leading  types  of  arborescent  dicotyledons  of  the  temper- 
ate latitudes.  The  flora  is  a  warm  temperate  one,  with  some  re- 
markable mixttires  of  sub-tropical  forms,  among  which  perhaps  the 
most  remarkable  are  Kaidocarpum  referred  to  the  Pandanece,  and 
such  exogens  as  Ficus  and  Cinnamomum. 

i....       2.  Tertiary.         ."j  ^.i 

4.  The  Unartok  series.  This  is  believed  to  be  Eocene.  It  con- 
sists of  sandstone,  which  appears  on  the  shores  of  Disco  Island,  and 


APPENDIX. 


283 


re- 

pe 
lid 


possibly  at  some  other  places  on  the  coast.  The  beds  rest  directly 
and  a[)paront!y  conformably  on  the  Upper  Cretaceous,  and  have  af- 
forded only  eleven  species  of  plants.  Magnolia  is  represented  by 
two  species,  Laurns  by  two,  Platanus  by  two,  and  one  of  these  said 
to  be  identical  with  a  species  found  by  Lesquereux  in  the  Laramie,* 
Viburnum,  Jiif/lans,  Querent,  each  by  one  species;  the  ubiquitous 
Sequoias  by  S.  Langsdorffii.  This  is  pretty  clearly  a  Lower  Laramie 
flora. 

5.  The  Atanel-erdluk  series,  consisting  of  shaly  beds,  with  lime- 
stone intercalated  between  great  sheets  of  basalt,  much  like  the 
Eocene  of  Antrim  and  the  Hebrides.  These  beds  have  yielded  187 
species,  principally  in  bands  and  concretions  of  siderite,  and  often 
in  a  good  state  of  preservation.  They  are  referred  to  the  Lower 
Miocene,  but,  as  explained  in  the  text,  the  flora  is  more  nearly  akin 
to  that  of  the  Eocene  of  Europe  and  the  Laramie  of  America.  The 
animal  fossils  are  chiefly  fresh-water  shells.  Onocka  settsibi/is, 
several  conifers,  as  I'axites  Olriki,  Taxodium  distichnm,  Glyptostro- 
bus  EurupcBus,  and  Sequoia  Langsdorffii,  and  42  of  the  dicotyledons 
are  recognised  as  found  also  in  American  localities.  Of  these,  a 
large  proportion  of  the  more  common  species  occur  in  the  Laramie 
of  the  Mackenzie  liiver  and  elsewhere  in  northwest  Canada,  and  in 
the  western  United  States.  It  is  quite  likely  also  that  several  spe- 
cies regarded  as  distinct  may  prove  to  1k>  identical. 

It  would  seem  that  throughout  the  whole  thickness  of  these 
Tertiary  beds  the  flora  is  similar,  so  that  it  is  probable  it  belongs  al- 
together to  the  Eocene  rather  than  to  the  IMioceno. 

No  indication  has  been  observed  of  any  period  of  cold  intervening 
between  the  Lower  Cretaceous  and  the  top  of  the  Tertiary  deposits, 
so  that,  in  all  the  vast  period  which  these  formations  represent,  the 
climate  of  Greenland  would  seem  to  have  been  temperate.  There 
is,  however,  as  is  the  case  farther  south,  evidence  of  a  gradual  dimi- 
nution of  temperature.  In  the  Lower  Cretaceous  the  probable  mean 
annual  temperature  in  latitude  71°  north  is  stated  as  21°  to  22° 
centigrade,  while  in  the  early  Tertiary  it  is  estimated  at  12°  centi- 
grade. Such  temperatures,  ranging  from  71°  to  ti',i°  of  Fahrenheit, 
represent  a  marvellously  warm  climate  for  so  high  a  latitude.  In 
point  of  fact,  however,  the  evidence  of  warm  climates  in  the  arctic 
regions,  in  the  Paheozoic  as  well  as  in  the  Mesozoic  and  early  Ter- 
tiary, should  perhaps  lead  us  to  conclude  that,  relatively  to  the  whole 
of  geological  time,  the  present  arctic  climate  is  unusually  severe,  and 


Viburnum  marginatum  of  Lesquereux. 


pin" 

mP 

Ul' 

284 


APPENDIX. 


that  a  temperate  climate  in  tbe  arctic  regions  has  throughout  geo- 
logical time  been  the  rule  rather  than  the  exception. 

III.-MINERALISATION   OP  FOSSIL  PLANTS. 

The  state  of  preservation  of  fossil  plants  has  been  roforred  to 
incidentally  in  several  places  in  the  text;  but  the  following  more 
definite  statements  may  be  of  service  to  the  reader. 

I.  Organic  remains  imV)ed(k'd  in  aqueous  deposits  may  occur  in. 
an  unchanged  condition,  or  only  more  or  less  altered  by  decay.  This 
is  often  the  case  with  such  enduring  substances  as  bark  and  wood, 
and  even  with  leaves,  which  appear  as  thin  carbonaceous  films  when 
the  layers  containing  them  are  split  open.  In  the  more  recent  de- 
posits such  remains  occur  little  modified,  or  perhaps  only  slightly 
changed  by  partial  decay  of  their  more  perishable  parts.  In  the 
older  formations,  however,  they  are  usually  found  in  a  more  or 
less  altered  condition,  in  which  their  original  substance  has  been 
wholly  or  in  part  changed  into  coaly,  or  bituminous,  or  anthracilic 
or  graphitic  matter,  so  that  leaves  are  sometimes  represented  by  stains 
of  graphite,  as  if  drawn  on  stone  with  a  lead-pencil.  Yet  even  in 
this  case  some  portion  of  the  original  substance  remains,  and  without 
any  introduction  of  foreign  material.  .• 

II.  On  the  other  hand,  such  remains  arc  often  mineralised  by  the 
filling  of  their  pores  or  the  replacement  of  their  tissues  with  mineral 
matter,  so  that  they  become  hard  and  stony,  and  sometimes  retain 
little  or  nothing  of  their  original  substance.  The  more  important 
of  these  changes,  in  so  far  as  they  affect  fossil  plants,  may  be  ar- 
ranged under  the  following  heads : 

(a)  Infiltration  of  mineral  matter  which  has  penetrated  the  pores 
of  the  fossil  in  a  state  of  solution.  Thus  the  pores  of  fossil  wood 
are  often  filled  with  calcite,  quartz,  oxide  of  iron,  or  sulphide  of  iron, 
while  the  woody  walls  of  the  cells  and  vessels  remain  in  a  carbonised 
state,  or  converted  into  coaly  matter.  When  wood  is  preserved  in 
this  way  it  has  a  hard  and  stony  aspect;  but  we  can  sometimes  dis- 
solve away  the  mineral  matter,  and  restore  the  vegetable  tissue  to  a 
condition  resembling  that  before  mineralisation.  Tiiis  is  especially 
the  case  when  calcite  is  the  mineralising  substance.  We  sometimes 
find,  on  microscopic  examination,  that  even  cavities  so  small  as  those 
of  vegetable  cells  and  vessels  have  been  filled  with  successive  coats 
of  different  kinds  of  mineral  matter. 

(6)  Organic  matters  may  be  entirely  replaced  by  mineral  sub- 
stances.   In  this  case  the  cavities  and  pores  have  been  first  filled, 


APPENDIX. 


285 


sub- 
illed, 


and  then — the  walls  or  solid  parts  being  removed  by  decay  or  solu- 
tion— mineral  matter,  either  similar  to  that  filling  the  cavities,  or 
ditroring  in  colour  or  composition,  has  been  introduced.  Silicifled 
wood  often  occurs  in  this  condition.  In  the  case  of  silicifled  wood, 
it  sometimes  hapi)cns  that  tlie  cavities  of  the  fibers  have  boon  filled 
with  silica,  and  the  wood  has  been  afterward  removed  l»y  decay, 
leaving  the  casts  of  the  tubular  fibers  as  a  loose  filamentous  sub- 
stance. Some  of  the  Tertiary  coniferous  woods  of  California  are  in 
this  state,  and  'ook  like  asbcstus,  though  they  show  the  minute 
markings  of  the  tissue  under  the  microscope.  In  the  case  of  silicilied 
or  agatized  woods,  it  would  seem  that  the  production  of  carbon  di- 
oxide from  the  decaying  wood  has  caused  the  deposition  of  silica  in 
its  place,  from  alkaiina  solutions  of  that  substance,  and  tlius  the 
carbon  has  been  replaced,  atom  by  atom,  by  silicon,  until  the  whole 
mass  has  been  silicifled,  yet  retaining  perfectly  its  structure. 

(c)  The  cavities  left  by  fossils  which  have  decayed  may  be  fllled 
with  clay,  sand,  or  other  foreign  matter,  and  this,  becoming  subse- 
quently hardened  into  stone,  nuiy  constitute  a  cast  of  the  fossils. 
Trunks  of  trees,  roots,  &c.,  arc  often  preserved  in  this  way,  appearing 
as  stony  casts,  often  with  the  outer  bark  of  the  plant  forming  a  car- 
bonaceous coating  on  their  surfaces.  In  connection  with  this  state 
may  be  mentioned  that  in  which,  the  wood  having  decayed,  an  entire 
trunk  has  been  flattened  so  as  to  appear  merely  as  a  compressed  film 
of  bark,  yet  retaining  its  markings ;  and  that  in  which  the  whole  of 
the  vegetable  nuitter  having  been  removed,  a  mere  impression  of 
the  form  remains. 

Fossils  preserved  in  either  of  the  modes,  (a)  or  (b),  usually  show 
more  or  less  of  their  minute  structures  under  the  microscope.  These 
may  be  observed : — (1)  By  breaking  off  small  splinters  or  flakes  and 
examining  them,  either  as  opaque  or  as  transparent  objects.  (2)  By 
treating  the  material  with  acids,  so  as  to  dissolve  out  the  mineral 
matters,  or  portions  of  them.  This  method  is  especially  applicable 
to  fossil  woods  mineralised  with  calcite  or  pyrite.  (3)  By  grinding 
thin  sections.  These  arc  flrst  polished  on  one  face  on  a  coarse  stone 
or  emery  hone,  and  then  on  a  fine  hone,  then  attached  by  the  polished 
face  to  glass  slips  with  a  transparent  cement  or  Canada  balsam,  and 
ground  on  the  opposite  face  until  they  become  so  thin  as  to  be  trans- 
lucent. In  most  cities  there  arc  lapidaries  who  propiire  slices  of  this 
kind;  but  tlie  amateur  can  readily  acipiire  the  art  by  a  little  prac- 
tice, and  the  necessary  appliances  can  be  obtained  through  dealers 
in  minerals  or  in  microscop'i  materials.  Very  convenient  cutting 
and  polishing  machines,  some  of  them  quite  small  and  portable,  are 
26 


28G 


APPENDIX. 


now  made  for  the  use  of  arnntcurs.  In  the  case  of  exogenous  woods 
three  sections  nre  necessary  to  exhibit  the  whole  of  the  structures. 
One  of  tliesc  should  l)c  transverse  and  two  longitudinal,  the  latter  in 
radial  and  tangential  planes. 


IV.-GENERAL  WORKS  ON  PAL^OBOTANF. 

In  the  text  frequent  reference  has  been  made  to  special  memoirs 
and  reports  on  the  fossil  plants  of  particular  regions  or  formations. 
There  are,  however,  some  general  books,  useful  to  students,  which 
may  be  mentioned  here.  Perhaps  the  most  important  is  Schimper's 
"  Traite  de  Paleontologie  Vegetale."  Very  useful  information  is 
also  contained  in  Renault's  "  Cours  de  Botanique  Fossile,"  and  in 
Balfour's  *'  Introduction  to  Pala^ontological  Botany,"  and  Nichol- 
son's "  Palieontology."  Unger's  "  Genera  et  Species,"  Brongniart's 
"  Histoire  des  Vegetaux  Fossiles,"  and  Lindley  and  Ilutton's  "  Fossil 
Flora,"  are  older  though  very  valuable  works.  Williamson's  "  Me- 
moirs," in  the  "  Philosophical  Transactions,"  have  greatly  advanced 
our  knowledge  of  the  structures  of  PaliPozoic  plants.  Lastly,  the 
"  Palteophytology  "  of  Schenk,  now  in  course  of  publication  in  Ger- 
man and  French,  in  connection  with  Zittel's  "  Palajontolcgy,"  is  an 
important  addition  to  manuals  of  the  subject. 


INDEX. 


Acer,  228. 

Acrogens,  6. 

Agassiz,  Prof.,  16, 

Alaska,  Flora  of,  245. 

Algae,  real  and  spurious,  26,  230. 

Amboy  clays.  Flora  of,  203, 
America,  Cretaceou."  of,  190. 
Angiosperms,  6. 
Annularia,  122. 
Anogens,  6. 
Antholithes,  132. 
Aporoxylon,  25. 
Araucarioxylon,  148. 
Aiaucarites,  134. 
Archacocalamites,  170. 
Archaeoptcris,  77,  85. 
Arctic  origin  of  plants,  221,  238. 
Arthrophycus,  30, 
Arthrostigma,  67. 
Asterophyllites,  78,  122,  170, 
Asteroptcris,  77,  85. 
Astropolithon,  30. 
Atane,  Tlants  of,  242,  281. 
Atanekerdluk,  Plants  of,  283, 
Australia,  Palaeozoic  flora  of,  147. 

•Tertiary  flora  of,  217. 

Bauhinia,  204. 
Bear  Island,  241. 
Betula,  198.  . 
Bilobites,  28. 


Borey  Tracoy,  Plants  of,  226. 
Brasenia,  207. 
Buckland,  Dr.,  179. 
Buthotrephis,  87. 

Calamitcs,  77,  123,  166. 
Calamodcndron,  125. 
Cambrian  flora,  20, 
Canada,  Brian  of,  108. 
Carboniferous  of,  1 10. 
Laramie  of,  209. 
Pleistocene  of,  227. 
Carbon  in  Laurentian,  9. 
Carboniferous  flora,  110, 
Carboniferous,  Climate  of,  138, 
of  Southern  Hemisphere,  147. 
Cardiocarpum,  82,  153, 
Carruthers,  Mr,,  24, 98, 180. 
On     modifications     of     modem 
plants,  225,  269. 
Carya,  196. 

Cauda-galli  fucoid,  106. 
Caulerpites,  29. 
Caulopteris,  75,  94. 
Clarke,  Prof,,  51. 
Climate,  Causes  of,  247. 
Climate  and  plants,  216,  220,  232. 
of  Carboniferous,  138, 
of  Cretaceous  and  Eocene,  216. 
of  Devonian,  47, 
of  Early  Mesozoic,  1 78. 


w 


J 


'iL- 


ilii 


PM 


i!t 


''ii  i 


,  ■  t  - 

>:(    :    ';>■"     i 

1  ii|i!  i  ■ 

■i  !'l 

:'1f  : 

288 


INDEX. 


Climate  and  plants  of  Laurcntian, 
17. 

of  rieiHtoceno,  227,  230. 

of  riiocenc,  22.3. 
Coal,  origin  of,  117,  130. 
Coniparirton  of  floras,  272. 
Coiniiositip,  2G0. 
Cone-lu-cone,  .36. 
ConiferoB,  Brian,  78,  90. 

Carboniferous,  134,  148.  - 

Mcsozoic,  etc.,  181. 
Cope,  Mr.,  215. 
Cordaites,  78,  130,  151. 
Corylus,  213. 
Crcpin,  M.,  99. 
Cretaceous,  Flora  of,  190. 

Climate  of,  216. 
Croll  on  climate,  252. 
Cromer,  Plants  of,  224. 
Cycad.><,  Mesozoic,  178. 
Cyclostigma,  157. 

Dadoxylon,  96,  134,  148. 
Dawson,  Dr.  G.  M.,  52,  210. 
Dolgado,  Prof.,  26. 
Dcndropliycus,  33. 
Derby,  Orville,  53. 
Devonian  flora,  45. 
Devonian  or  Brian,  107,  279. 

Climate  of,  47. 
Dicotyledons,  Cretaceous,  192. 

Table  of,  192.  ,    ^ 

Dictyolites.  33. 
Dictyospongia,  39. 
Disco,  Bxotic  plants  at,  256. 

Flora  of,  245,  282. 
Drepanophycus,  39. 
Drosera,  228. 
Dunvegan  beds,  244. 

Eocene,  Flora  of,  208,  214.    ^ 
Climate  of,  216. 

Eophyton,  81.   >    .  '•    ^.    ■      ■    v 


Eoptcrifi,  72. 

Eozoon  of  Laurcntian,  9. 
Eipiisotum,  170,  230. 
Brian  Hora,  45,  279. 

Climate  of,  47. 
Erian  or  Devonian,  107. 
Ettingshauscn,  Dr.,  187,  215. 
Exogcns,  Cretaceous,  192. 

Tertiary,  213,  224. 

FaguB,  196,  197. 
Ferns,  Brian,  72. 

Carboniferous,  120,  171. 

Fructification  of,  128. 

Stems  of,  90,  129. 

Tertiary,  212. 
Filiccs,  72,  126,  171. 
Flora  of  Cambrian,  26. 

of  Carboniferous,  110,  274. 

of  Cretaceous,  190. 

of  Early  Mesozoic,  175. 

of  Brian,  45,  279. 

of  Jurassic,  177,  186. 

of  Laramie,  209. 

of  Laurcntian,  8. 

of  Miocene,  220,  223. 

of  Modem,  219. 

of  Permian,  274. 

of  Pleistocene,  223,  227. 

of  Tertiary,  191,  208,  214,  219. 
Fontaine,  Prof.,  130,  176. 
Fontinalis,  230. 
.  ort  Union  beds,  210. 
Fucoids,  27. 

Gardner,  Mr.  Starkic,  212. 
Gcinitz,  Dr.,  174. 

Geological  formations,  Table  of,  4. 
Glossopteris,  147. 
G'yptodendron,  25.  ^ 

Glyptostrobup,  194.  •  ■      '    - 

Goeppert,  Dr.,  99. 
Grant,  Col.,  36.  .    . 


I 


INDEX. 


289 


[19. 


f,4. 


Graphite  from  plants,  8. 

Gray,  Dr.,  Origin  of  floras,  223,  237. 

Greenland,  Climate  of,  210. 

Fossil  flora  of,  2-17. 
(iiiliclniiteH,  .35. 
Gymnosperms,  G. 

Hallserites,  Sflf. 

Hartt,  Prof.,  53. 

Ileer,  Dr.,  108,  181. 

Ilclderbcrg  period.  Sea  of,  250. 

Ileterangium,  77. 

lliekfl,  Dr.,  21. 

Hunt,  Dr.  Stcrry,  13,  143. 

Huxley,  Prof,,  63. 

Ilymenuca,  2<>4. 

Insects,  Erian,  83. 

Juglans,  196. 
Jurassic  flora,  177. 

Kainozoic  flora,  191,  208,  214,  219. 
Kidston,  Mr.  R.,  128,  273. 
King,  Mr.  Clarence,  211. 
Komc,  Plants  of,  242,  281. 

Laramie  flora,  209,  215. 
Laurentian  plants,  8. 
Laurcntian,  Climate  of,  17. 
Lauropliyllam,  193. 
Laws  of  introduction  of  plants,  237, 

260. 
Leda  clay,  Flora  of,  232. 
Lepidodendron,  120,  156,  162. 
Lepidophloios,  121,  157,  165. 
Leptophleum,  157. 
Lesquereux,  Mr.  L.,  169,  214. 
Licrophyeus,  30. 
Lignitic  series  of  America,  208. 
Liquidambar,  197. 
Liriodendron,  199. 
Lower  Carboniferous  flora,  277. 
Logan,  Sir  W.,  48. 
Lyell  on  cliraftte,  249. 


Magnolia,  200. 
McConncIl,  Mr.,  209. 
McNab,  Prof.,  169. 
Megaloptcris,  70, 
Mogaphyton,  129. 
Mesozoic  flora,  175. 

Climate  of,  178. 
Migrations  of  plants,  240,  24S. 
Miller,  llugli,  98. 
Miocene  flora,  220. 
Miocene,  Supposed,  242. 
Modern  flora,  219. 
Modern  plants,  liow  modified,  269. 
Moditications  of  plants,  266. 

Nathorst,  Dr.,  26,  1 96. 
NeniatodcndreiP,  25. 
Nematophycus,  23, 
Nematopliyton,  21,  22,  42. 
Newberry,  Dr.,  200,  203,  214. 
Newfoundland,  Fossil  plants  of,  242. 
Newton,  Mr.,  52, 
Nicholson,  Dr.  A.,  20. 
Niobrara  series,  243,  246. 
Noeggcrathia,  130. 
Northern  origin  of  plants,  238. 

Origin  of  plants,  237. 
Or  ton.  Prof.,  51. 

Pachytheca,  21. 
Pp'.ccanthus,  205. 
Palajochorda,  30. 
Palaeophycus,  30,  88. 
Palaeozoic  floras  compared,  273. 
Palms,  188,  194. 
Pandanus,  188.       ,  .    * 
Patootbeds,  282. 
Peach,  Mr.,  98. 
Petroleum,  Origin  of,  56. 
Phymatodcrma,  29. 
Plants,  Classification  of,  6. 
Platanus,  198. 
Platyphyllum,  74. 


I'  '.'1 


§ 


290  INDEX. 

Pleistocene  climate,  227,  230. 
Pleistocene  llora,  223,  227. 
Pliocene  climate,  223. 
Podozamitcs,  178. 
Poles,  Supposed  change  of,  248. 
Populus,  191,  228. 
Potamogeton,  229. 
Potcntilla,  228. 
Protannularia,  21. 
Protichnites,  27. 
Protophyllum,  199. 
Protosalvinia,  62, 
Protostigma,  20. 
Prototaxitcs,  21. 
Psaronius,  93. 
Psilophvton,  64. 
Ptilophyton,  02,  86. 

Quercus,  197. 

Rhizocarps,  48. 
Piiil-marks,  33. 
Rusichnites,  28. 

Saccamina,  57. 
Salislmria,  lt<0. 
Salter,  Mr.,  98.  ' 

Salvinia,  54. 

Saporta.  Count  de,  26,  193. 
Saportea,  57.  '    >   . 

Sassafras,  199. 
Scalariform  tissue,  70. 
Schimpcr,  Dr.,  116,  169,  208. 
Scolithus,  30.         ...  ,.    .  ' 

Scottish  Devonian,  98. 
Sequoia,  181.  ,        • 

Shrinkage  cracks,  33. 
Sigillaria,  71,  112,  164. 
Southern  Hemisphere,  217,  273. 
Carboniferous  in,  147. 


Southern  Hemisphere,  Tertiary  in, 

217. 
Sphenophyllum,  61,  122,  171. 
Spirophyton,  38. 
Spitzbergen,  241. 
Sterculitcs,  193, 
Sternbergia,  137,  152. 
Stigmaria,  115. 

Stur,  Dr.,  on  Sigillaria,  116.       -  ^ 
Symphorocarpus,  214.  .       r 

Syringodendron,  156.         .   .      ; 
Syringoxylon,  82. 

Table  of  formations,  4. 

Tasmania,  Fossil  plants  of,  217, 246. 

Tasmanite,  67. 

Tertiary  period.  Flora  of,  191,  208, 

214,  219. 
Tertiary  of  Australia,  217. 
Thallogens,  6. 
Thomas,  Mr.,  51. 

Thuja,  213,  229.    '  ^    ■ 

Time,  Geological,  5. 
Trapa,  196.  -     '    • 

Tree-ferns,  90,  129.       ..  .  ,   - 
Triassic  flora,  176. 
Trigonocarpum,  130,  153. 
Tyndall,  Prof.,  138.      , 

Ulrich,  Prof.,  57.  ' 

Unartok  beds,  281.  ' 

Ursa  stage  of  Hccr,  108,  241. 

Walchia,  134,  138. 

Ward,  iMr.  L.  T.,  192,  212,  215.       ■ 

Wethcrcd,  Mr.  E.,  52. 

White,  Dr.,  215. 

Williams,  Prof.,  51. 

Williamson,  Dr.,  26,  81,  71,  167. 

Williamsonia,  188. 


THE   END. 


til 


in, 


D,  APPLETON  &  GO.'S  PUBUOATIONS. 


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